Remodel the Model

- The configuration and crypto model is now entirely independent
  of Android classes other than Nullable and TextUtils.
- Model classes are immutable and use builders that enforce the
  appropriate optional/required attributes.
- The Android config proxies (for Parcelable and databinding) are
  moved to the Android side of the codebase, and are designed to be
  safe for two-way databinding. This allows proper observability in
  TunnelDetailFragment.
- Various robustness fixes and documentation updates to helper classes.

47 files changed, 2025 insertions, 1283 deletions

diff --git a/.idea/copyright/Default.xml b/.idea/copyright/Default.xml
index 9149bd43..cb646393 100644
--- a/.idea/copyright/Default.xml
+++ b/.idea/copyright/Default.xml
@@ -1,6 +1,6 @@
 <component name="CopyrightManager">
   <copyright>
-    <option name="notice" value="Copyright © &amp;#36;today.year Firstname Lastname &lt;email@example.org&gt;&#10;SPDX-License-Identifier: Apache-2.0
+    <option name="notice" value="Copyright © &amp;#36;today.year WireGuard LLC. All Rights Reserved.&#10;SPDX-License-Identifier: Apache-2.0" />
     <option name="myName" value="Default" />
   </copyright>
 </component>
diff --git a/.idea/copyright/profiles_settings.xml b/.idea/copyright/profiles_settings.xml
index 53146971..eb839538 100644
--- a/.idea/copyright/profiles_settings.xml
+++ b/.idea/copyright/profiles_settings.xml
@@ -1,3 +1,3 @@
 <component name="CopyrightManager">
-  <settings default="GPL-2.0-or-later" />
-</component>
\ No newline at end of file
+  <settings default="Default" />
+</component>
diff --git a/.idea/inspectionProfiles/Default.xml b/.idea/inspectionProfiles/Default.xml
index 6dd07e6e..f048a118 100644
--- a/.idea/inspectionProfiles/Default.xml
+++ b/.idea/inspectionProfiles/Default.xml
@@ -385,7 +385,6 @@
       <option name="ignorePrivateMethods" value="true" />
     </inspection_tool>
     <inspection_tool class="ReturnOfDateField" enabled="false" level="WARNING" enabled_by_default="false" />
-    <inspection_tool class="ReturnOfInnerClass" enabled="true" level="WARNING" enabled_by_default="true" />
     <inspection_tool class="ScalarTypeRequired" enabled="true" level="ERROR" enabled_by_default="true" />
     <inspection_tool class="SerializableClassInSecureContext" enabled="false" level="WARNING" enabled_by_default="false" />
     <inspection_tool class="SetReplaceableByEnumSet" enabled="true" level="WARNING" enabled_by_default="true" />
diff --git a/app/build.gradle b/app/build.gradle
index fb30d2a2..f0ed927c 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -65,12 +65,13 @@ android {
 }
 
 ext {
+    acraVersion = '5.2.0-rc2'
     databindingVersion = '3.1.3'
-    supportLibsVersion = '27.1.1'
-    streamsupportVersion = '1.6.0'
     jsr305Version = '3.0.2'
+    streamsupportVersion = '1.6.0'
+    supportLibsVersion = '28.0.0'
+    threetenabpVersion = '1.1.1'
     zxingEmbeddedVersion = '3.6.0'
-    acraVersion = '5.2.0-rc2'
 }
 
 dependencies {
@@ -81,6 +82,7 @@ dependencies {
     implementation "com.android.support:preference-v14:$supportLibsVersion"
     implementation "com.android.support:support-annotations:$supportLibsVersion"
     implementation "com.google.code.findbugs:jsr305:$jsr305Version"
+    implementation "com.jakewharton.threetenabp:threetenabp:$threetenabpVersion"
     implementation "com.journeyapps:zxing-android-embedded:$zxingEmbeddedVersion"
     implementation "net.sourceforge.streamsupport:android-retrofuture:$streamsupportVersion"
     implementation "net.sourceforge.streamsupport:android-retrostreams:$streamsupportVersion"
diff --git a/app/src/main/java/com/wireguard/android/backend/GoBackend.java b/app/src/main/java/com/wireguard/android/backend/GoBackend.java
index 295df9d0..97cf0f8e 100644
--- a/app/src/main/java/com/wireguard/android/backend/GoBackend.java
+++ b/app/src/main/java/com/wireguard/android/backend/GoBackend.java
@@ -22,13 +22,10 @@ import com.wireguard.android.util.ExceptionLoggers;
 import com.wireguard.android.util.SharedLibraryLoader;
 import com.wireguard.config.Config;
 import com.wireguard.config.InetNetwork;
-import com.wireguard.config.Interface;
 import com.wireguard.config.Peer;
-import com.wireguard.crypto.KeyEncoding;
 
 import java.net.InetAddress;
 import java.util.Collections;
-import java.util.Formatter;
 import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.TimeUnit;
@@ -146,29 +143,7 @@ public final class GoBackend implements Backend {
             }
 
             // Build config
-            final Interface iface = config.getInterface();
-            final String goConfig;
-            try (final Formatter fmt = new Formatter(new StringBuilder())) {
-                fmt.format("replace_peers=true\n");
-                if (iface.getPrivateKey() != null)
-                    fmt.format("private_key=%s\n", KeyEncoding.keyToHex(KeyEncoding.keyFromBase64(iface.getPrivateKey())));
-                if (iface.getListenPort() != 0)
-                    fmt.format("listen_port=%d\n", config.getInterface().getListenPort());
-                for (final Peer peer : config.getPeers()) {
-                    if (peer.getPublicKey() != null)
-                        fmt.format("public_key=%s\n", KeyEncoding.keyToHex(KeyEncoding.keyFromBase64(peer.getPublicKey())));
-                    if (peer.getPreSharedKey() != null)
-                        fmt.format("preshared_key=%s\n", KeyEncoding.keyToHex(KeyEncoding.keyFromBase64(peer.getPreSharedKey())));
-                    if (peer.getEndpoint() != null)
-                        fmt.format("endpoint=%s\n", peer.getResolvedEndpointString());
-                    if (peer.getPersistentKeepalive() != 0)
-                        fmt.format("persistent_keepalive_interval=%d\n", peer.getPersistentKeepalive());
-                    for (final InetNetwork addr : peer.getAllowedIPs()) {
-                        fmt.format("allowed_ip=%s\n", addr.toString());
-                    }
-                }
-                goConfig = fmt.toString();
-            }
+            final String goConfig = config.toWgUserspaceString();
 
             // Create the vpn tunnel with android API
             final VpnService.Builder builder = service.getBuilder();
@@ -184,18 +159,15 @@ public final class GoBackend implements Backend {
             for (final InetNetwork addr : config.getInterface().getAddresses())
                 builder.addAddress(addr.getAddress(), addr.getMask());
 
-            for (final InetAddress addr : config.getInterface().getDnses())
+            for (final InetAddress addr : config.getInterface().getDnsServers())
                 builder.addDnsServer(addr.getHostAddress());
 
             for (final Peer peer : config.getPeers()) {
-                for (final InetNetwork addr : peer.getAllowedIPs())
+                for (final InetNetwork addr : peer.getAllowedIps())
                     builder.addRoute(addr.getAddress(), addr.getMask());
             }
 
-            int mtu = config.getInterface().getMtu();
-            if (mtu == 0)
-                mtu = 1280;
-            builder.setMtu(mtu);
+            builder.setMtu(config.getInterface().getMtu().orElse(1280));
 
             builder.setBlocking(true);
             try (final ParcelFileDescriptor tun = builder.establish()) {
diff --git a/app/src/main/java/com/wireguard/android/backend/WgQuickBackend.java b/app/src/main/java/com/wireguard/android/backend/WgQuickBackend.java
index bfc363a4..68799057 100644
--- a/app/src/main/java/com/wireguard/android/backend/WgQuickBackend.java
+++ b/app/src/main/java/com/wireguard/android/backend/WgQuickBackend.java
@@ -114,7 +114,7 @@ public final class WgQuickBackend implements Backend {
 
         final File tempFile = new File(localTemporaryDir, tunnel.getName() + ".conf");
         try (final FileOutputStream stream = new FileOutputStream(tempFile, false)) {
-            stream.write(config.toString().getBytes(StandardCharsets.UTF_8));
+            stream.write(config.toWgQuickString().getBytes(StandardCharsets.UTF_8));
         }
         String command = String.format("wg-quick %s '%s'",
                 state.toString().toLowerCase(), tempFile.getAbsolutePath());
diff --git a/app/src/main/java/com/wireguard/android/configStore/FileConfigStore.java b/app/src/main/java/com/wireguard/android/configStore/FileConfigStore.java
index 0e66dab8..654cb48f 100644
--- a/app/src/main/java/com/wireguard/android/configStore/FileConfigStore.java
+++ b/app/src/main/java/com/wireguard/android/configStore/FileConfigStore.java
@@ -9,6 +9,7 @@ import android.content.Context;
 import android.util.Log;
 
 import com.wireguard.config.Config;
+import com.wireguard.config.ParseException;
 
 import java.io.File;
 import java.io.FileInputStream;
@@ -41,7 +42,7 @@ public final class FileConfigStore implements ConfigStore {
         if (!file.createNewFile())
             throw new IOException("Configuration file " + file.getName() + " already exists");
         try (final FileOutputStream stream = new FileOutputStream(file, false)) {
-            stream.write(config.toString().getBytes(StandardCharsets.UTF_8));
+            stream.write(config.toWgQuickString().getBytes(StandardCharsets.UTF_8));
         }
         return config;
     }
@@ -67,9 +68,9 @@ public final class FileConfigStore implements ConfigStore {
     }
 
     @Override
-    public Config load(final String name) throws IOException {
+    public Config load(final String name) throws IOException, ParseException {
         try (final FileInputStream stream = new FileInputStream(fileFor(name))) {
-            return Config.from(stream);
+            return Config.parse(stream);
         }
     }
 
@@ -94,7 +95,7 @@ public final class FileConfigStore implements ConfigStore {
         if (!file.isFile())
             throw new FileNotFoundException("Configuration file " + file.getName() + " not found");
         try (final FileOutputStream stream = new FileOutputStream(file, false)) {
-            stream.write(config.toString().getBytes(StandardCharsets.UTF_8));
+            stream.write(config.toWgQuickString().getBytes(StandardCharsets.UTF_8));
         }
         return config;
     }
diff --git a/app/src/main/java/com/wireguard/android/databinding/BindingAdapters.java b/app/src/main/java/com/wireguard/android/databinding/BindingAdapters.java
index 629f99e5..fe01bf10 100644
--- a/app/src/main/java/com/wireguard/android/databinding/BindingAdapters.java
+++ b/app/src/main/java/com/wireguard/android/databinding/BindingAdapters.java
@@ -6,21 +6,30 @@
 package com.wireguard.android.databinding;
 
 import android.databinding.BindingAdapter;
+import android.databinding.DataBindingUtil;
 import android.databinding.ObservableList;
+import android.databinding.ViewDataBinding;
 import android.databinding.adapters.ListenerUtil;
+import android.support.annotation.Nullable;
 import android.support.v7.widget.LinearLayoutManager;
 import android.support.v7.widget.RecyclerView;
 import android.text.InputFilter;
+import android.view.LayoutInflater;
 import android.widget.LinearLayout;
 import android.widget.TextView;
 
+import com.wireguard.android.BR;
 import com.wireguard.android.R;
 import com.wireguard.android.databinding.ObservableKeyedRecyclerViewAdapter.RowConfigurationHandler;
 import com.wireguard.android.util.ObservableKeyedList;
 import com.wireguard.android.widget.ToggleSwitch;
 import com.wireguard.android.widget.ToggleSwitch.OnBeforeCheckedChangeListener;
+import com.wireguard.config.Attribute;
+import com.wireguard.config.InetNetwork;
 import com.wireguard.util.Keyed;
 
+import java9.util.Optional;
+
 /**
  * Static methods for use by generated code in the Android data binding library.
  */
@@ -42,9 +51,10 @@ public final class BindingAdapters {
     }
 
     @BindingAdapter({"items", "layout"})
-    public static <E> void setItems(final LinearLayout view,
-                                    final ObservableList<E> oldList, final int oldLayoutId,
-                                    final ObservableList<E> newList, final int newLayoutId) {
+    public static <E>
+    void setItems(final LinearLayout view,
+                  @Nullable final ObservableList<E> oldList, final int oldLayoutId,
+                  @Nullable final ObservableList<E> newList, final int newLayoutId) {
         if (oldList == newList && oldLayoutId == newLayoutId)
             return;
         ItemChangeListener<E> listener = ListenerUtil.getListener(view, R.id.item_change_listener);
@@ -66,11 +76,34 @@ public final class BindingAdapters {
         listener.setList(newList);
     }
 
+    @BindingAdapter({"items", "layout"})
+    public static <E>
+    void setItems(final LinearLayout view,
+                  @Nullable final Iterable<E> oldList, final int oldLayoutId,
+                  @Nullable final Iterable<E> newList, final int newLayoutId) {
+        if (oldList == newList && oldLayoutId == newLayoutId)
+            return;
+        view.removeAllViews();
+        if (newList == null)
+            return;
+        final LayoutInflater layoutInflater = LayoutInflater.from(view.getContext());
+        for (final E item : newList) {
+            final ViewDataBinding binding =
+                    DataBindingUtil.inflate(layoutInflater, newLayoutId, view, false);
+            binding.setVariable(BR.collection, newList);
+            binding.setVariable(BR.item, item);
+            binding.executePendingBindings();
+            view.addView(binding.getRoot());
+        }
+    }
+
     @BindingAdapter(requireAll = false, value = {"items", "layout", "configurationHandler"})
     public static <K, E extends Keyed<? extends K>>
     void setItems(final RecyclerView view,
-                  final ObservableKeyedList<K, E> oldList, final int oldLayoutId, final RowConfigurationHandler oldRowConfigurationHandler,
-                  final ObservableKeyedList<K, E> newList, final int newLayoutId, final RowConfigurationHandler newRowConfigurationHandler) {
+                  @Nullable final ObservableKeyedList<K, E> oldList, final int oldLayoutId,
+                  final RowConfigurationHandler oldRowConfigurationHandler,
+                  @Nullable final ObservableKeyedList<K, E> newList, final int newLayoutId,
+                  final RowConfigurationHandler newRowConfigurationHandler) {
         if (view.getLayoutManager() == null)
             view.setLayoutManager(new LinearLayoutManager(view.getContext(), RecyclerView.VERTICAL, false));
 
@@ -103,4 +136,13 @@ public final class BindingAdapters {
         view.setOnBeforeCheckedChangeListener(listener);
     }
 
+    @BindingAdapter("android:text")
+    public static void setText(final TextView view, final Optional<?> text) {
+        view.setText(text.map(Object::toString).orElse(""));
+    }
+
+    @BindingAdapter("android:text")
+    public static void setText(final TextView view, @Nullable final Iterable<InetNetwork> networks) {
+        view.setText(networks != null ? Attribute.join(networks) : "");
+    }
 }
diff --git a/app/src/main/java/com/wireguard/android/databinding/ObservableKeyedRecyclerViewAdapter.java b/app/src/main/java/com/wireguard/android/databinding/ObservableKeyedRecyclerViewAdapter.java
index 26e7687f..5bfa64f1 100644
--- a/app/src/main/java/com/wireguard/android/databinding/ObservableKeyedRecyclerViewAdapter.java
+++ b/app/src/main/java/com/wireguard/android/databinding/ObservableKeyedRecyclerViewAdapter.java
@@ -73,7 +73,7 @@ public class ObservableKeyedRecyclerViewAdapter<K, E extends Keyed<? extends K>>
         holder.binding.executePendingBindings();
 
         if (rowConfigurationHandler != null) {
-            E item = getItem(position);
+            final E item = getItem(position);
             if (item != null) {
                 rowConfigurationHandler.onConfigureRow(holder.binding, item, position);
             }
diff --git a/app/src/main/java/com/wireguard/android/fragment/AppListDialogFragment.java b/app/src/main/java/com/wireguard/android/fragment/AppListDialogFragment.java
index 8bf5a22d..20633c3e 100644
--- a/app/src/main/java/com/wireguard/android/fragment/AppListDialogFragment.java
+++ b/app/src/main/java/com/wireguard/android/fragment/AppListDialogFragment.java
@@ -27,19 +27,21 @@ import com.wireguard.android.util.ObservableKeyedArrayList;
 import com.wireguard.android.util.ObservableKeyedList;
 
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 
+import java9.util.Comparators;
+
 public class AppListDialogFragment extends DialogFragment {
 
     private static final String KEY_EXCLUDED_APPS = "excludedApps";
     private final ObservableKeyedList<String, ApplicationData> appData = new ObservableKeyedArrayList<>();
-    private List<String> currentlyExcludedApps;
+    @Nullable private List<String> currentlyExcludedApps;
 
-    public static <T extends Fragment & AppExclusionListener> AppListDialogFragment newInstance(final String[] excludedApps, final T target) {
+    public static <T extends Fragment & AppExclusionListener>
+    AppListDialogFragment newInstance(final ArrayList<String> excludedApps, final T target) {
         final Bundle extras = new Bundle();
-        extras.putStringArray(KEY_EXCLUDED_APPS, excludedApps);
+        extras.putStringArrayList(KEY_EXCLUDED_APPS, excludedApps);
         final AppListDialogFragment fragment = new AppListDialogFragment();
         fragment.setTargetFragment(target, 0);
         fragment.setArguments(extras);
@@ -64,7 +66,7 @@ public class AppListDialogFragment extends DialogFragment {
                 appData.add(new ApplicationData(resolveInfo.loadIcon(pm), resolveInfo.loadLabel(pm).toString(), packageName, currentlyExcludedApps.contains(packageName)));
             }
 
-            Collections.sort(appData, (lhs, rhs) -> lhs.getName().toLowerCase().compareTo(rhs.getName().toLowerCase()));
+            Collections.sort(appData, Comparators.comparing(ApplicationData::getName, String.CASE_INSENSITIVE_ORDER));
             return appData;
         }).whenComplete(((data, throwable) -> {
             if (data != null) {
@@ -82,12 +84,11 @@ public class AppListDialogFragment extends DialogFragment {
     @Override
     public void onCreate(@Nullable final Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
-
-        currentlyExcludedApps = Arrays.asList(getArguments().getStringArray(KEY_EXCLUDED_APPS));
+        currentlyExcludedApps = getArguments().getStringArrayList(KEY_EXCLUDED_APPS);
     }
 
     @Override
-    public Dialog onCreateDialog(final Bundle savedInstanceState) {
+    public Dialog onCreateDialog(@Nullable final Bundle savedInstanceState) {
         final AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(getActivity());
         alertDialogBuilder.setTitle(R.string.excluded_applications);
 
diff --git a/app/src/main/java/com/wireguard/android/fragment/ConfigNamingDialogFragment.java b/app/src/main/java/com/wireguard/android/fragment/ConfigNamingDialogFragment.java
index 83799818..0931868e 100644
--- a/app/src/main/java/com/wireguard/android/fragment/ConfigNamingDialogFragment.java
+++ b/app/src/main/java/com/wireguard/android/fragment/ConfigNamingDialogFragment.java
@@ -19,8 +19,11 @@ import com.wireguard.android.Application;
 import com.wireguard.android.R;
 import com.wireguard.android.databinding.ConfigNamingDialogFragmentBinding;
 import com.wireguard.config.Config;
+import com.wireguard.config.ParseException;
 
+import java.io.ByteArrayInputStream;
 import java.io.IOException;
+import java.nio.charset.StandardCharsets;
 import java.util.Objects;
 
 public class ConfigNamingDialogFragment extends DialogFragment {
@@ -63,8 +66,8 @@ public class ConfigNamingDialogFragment extends DialogFragment {
         super.onCreate(savedInstanceState);
 
         try {
-            config = Config.from(getArguments().getString(KEY_CONFIG_TEXT));
-        } catch (final IOException exception) {
+            config = Config.parse(new ByteArrayInputStream(getArguments().getString(KEY_CONFIG_TEXT).getBytes(StandardCharsets.UTF_8)));
+        } catch (final IOException | ParseException exception) {
             throw new RuntimeException("Invalid config passed to " + getClass().getSimpleName(), exception);
         }
     }
diff --git a/app/src/main/java/com/wireguard/android/fragment/TunnelDetailFragment.java b/app/src/main/java/com/wireguard/android/fragment/TunnelDetailFragment.java
index fcc601f3..b4e7202f 100644
--- a/app/src/main/java/com/wireguard/android/fragment/TunnelDetailFragment.java
+++ b/app/src/main/java/com/wireguard/android/fragment/TunnelDetailFragment.java
@@ -16,7 +16,6 @@ import android.view.ViewGroup;
 import com.wireguard.android.R;
 import com.wireguard.android.databinding.TunnelDetailFragmentBinding;
 import com.wireguard.android.model.Tunnel;
-import com.wireguard.config.Config;
 
 /**
  * Fragment that shows details about a specific tunnel.
@@ -25,12 +24,6 @@ import com.wireguard.config.Config;
 public class TunnelDetailFragment extends BaseFragment {
     @Nullable private TunnelDetailFragmentBinding binding;
 
-    private void onConfigLoaded(final String name, final Config config) {
-        if (binding != null) {
-            binding.setConfig(new Config.Observable(config, name));
-        }
-    }
-
     @Override
     public void onCreate(@Nullable final Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
@@ -65,7 +58,7 @@ public class TunnelDetailFragment extends BaseFragment {
         if (newTunnel == null)
             binding.setConfig(null);
         else
-            newTunnel.getConfigAsync().thenAccept(a -> onConfigLoaded(newTunnel.getName(), a));
+            newTunnel.getConfigAsync().thenAccept(binding::setConfig);
     }
 
     @Override
diff --git a/app/src/main/java/com/wireguard/android/fragment/TunnelEditorFragment.java b/app/src/main/java/com/wireguard/android/fragment/TunnelEditorFragment.java
index 8f319e1e..f1250e64 100644
--- a/app/src/main/java/com/wireguard/android/fragment/TunnelEditorFragment.java
+++ b/app/src/main/java/com/wireguard/android/fragment/TunnelEditorFragment.java
@@ -7,7 +7,6 @@ package com.wireguard.android.fragment;
 
 import android.app.Activity;
 import android.content.Context;
-import android.databinding.Observable;
 import android.databinding.ObservableList;
 import android.os.Bundle;
 import android.support.annotation.Nullable;
@@ -24,19 +23,16 @@ import android.view.inputmethod.InputMethodManager;
 import android.widget.Toast;
 
 import com.wireguard.android.Application;
-import com.wireguard.android.BR;
 import com.wireguard.android.R;
 import com.wireguard.android.databinding.TunnelEditorFragmentBinding;
 import com.wireguard.android.fragment.AppListDialogFragment.AppExclusionListener;
 import com.wireguard.android.model.Tunnel;
 import com.wireguard.android.model.TunnelManager;
 import com.wireguard.android.util.ExceptionLoggers;
-import com.wireguard.config.Attribute;
+import com.wireguard.android.viewmodel.ConfigProxy;
 import com.wireguard.config.Config;
-import com.wireguard.config.Peer;
 
 import java.util.ArrayList;
-import java.util.Collection;
 import java.util.List;
 import java.util.Objects;
 
@@ -48,64 +44,13 @@ public class TunnelEditorFragment extends BaseFragment implements AppExclusionLi
     private static final String KEY_LOCAL_CONFIG = "local_config";
     private static final String KEY_ORIGINAL_NAME = "original_name";
     private static final String TAG = "WireGuard/" + TunnelEditorFragment.class.getSimpleName();
-    private final Collection<Object> breakObjectOrientedLayeringHandlerReceivers = new ArrayList<>();
-    @Nullable private TunnelEditorFragmentBinding binding;
-    private final Observable.OnPropertyChangedCallback breakObjectOrientedLayeringHandler = new Observable.OnPropertyChangedCallback() {
-        @Override
-        public void onPropertyChanged(final Observable sender, final int propertyId) {
-            if (binding == null)
-                return;
-            final Config.Observable config = binding.getConfig();
-            if (config == null)
-                return;
-            if (propertyId == BR.config) {
-                config.addOnPropertyChangedCallback(breakObjectOrientedLayeringHandler);
-                breakObjectOrientedLayeringHandlerReceivers.add(config);
-                config.getInterfaceSection().addOnPropertyChangedCallback(breakObjectOrientedLayeringHandler);
-                breakObjectOrientedLayeringHandlerReceivers.add(config.getInterfaceSection());
-                config.getPeers().addOnListChangedCallback(breakObjectListOrientedLayeringHandler);
-                breakObjectOrientedLayeringHandlerReceivers.add(config.getPeers());
-            } else if (propertyId == BR.dnses || propertyId == BR.peers)
-                ;
-            else
-                return;
-            final int numSiblings = config.getPeers().size() - 1;
-            for (final Peer.Observable peer : config.getPeers()) {
-                peer.setInterfaceDNSRoutes(config.getInterfaceSection().getDnses());
-                peer.setNumSiblings(numSiblings);
-            }
-        }
-    };
-    private final ObservableList.OnListChangedCallback<? extends ObservableList<Peer.Observable>> breakObjectListOrientedLayeringHandler = new ObservableList.OnListChangedCallback<ObservableList<Peer.Observable>>() {
-        @Override
-        public void onChanged(final ObservableList<Peer.Observable> sender) {
-        }
-
-        @Override
-        public void onItemRangeChanged(final ObservableList<Peer.Observable> sender, final int positionStart, final int itemCount) {
-        }
-
-        @Override
-        public void onItemRangeInserted(final ObservableList<Peer.Observable> sender, final int positionStart, final int itemCount) {
-            if (binding != null)
-                breakObjectOrientedLayeringHandler.onPropertyChanged(binding.getConfig(), BR.peers);
-        }
 
-        @Override
-        public void onItemRangeMoved(final ObservableList<Peer.Observable> sender, final int fromPosition, final int toPosition, final int itemCount) {
-        }
-
-        @Override
-        public void onItemRangeRemoved(final ObservableList<Peer.Observable> sender, final int positionStart, final int itemCount) {
-            if (binding != null)
-                breakObjectOrientedLayeringHandler.onPropertyChanged(binding.getConfig(), BR.peers);
-        }
-    };
+    @Nullable private TunnelEditorFragmentBinding binding;
     @Nullable private Tunnel tunnel;
 
-    private void onConfigLoaded(final String name, final Config config) {
+    private void onConfigLoaded(final Config config) {
         if (binding != null) {
-            binding.setConfig(new Config.Observable(config, name));
+            binding.setConfig(new ConfigProxy(config));
         }
     }
 
@@ -143,29 +88,23 @@ public class TunnelEditorFragment extends BaseFragment implements AppExclusionLi
                              @Nullable final Bundle savedInstanceState) {
         super.onCreateView(inflater, container, savedInstanceState);
         binding = TunnelEditorFragmentBinding.inflate(inflater, container, false);
-        binding.addOnPropertyChangedCallback(breakObjectOrientedLayeringHandler);
-        breakObjectOrientedLayeringHandlerReceivers.add(binding);
         binding.executePendingBindings();
         return binding.getRoot();
     }
 
-    @SuppressWarnings("unchecked")
     @Override
     public void onDestroyView() {
         binding = null;
-        for (final Object o : breakObjectOrientedLayeringHandlerReceivers) {
-            if (o instanceof Observable)
-                ((Observable) o).removeOnPropertyChangedCallback(breakObjectOrientedLayeringHandler);
-            else if (o instanceof ObservableList)
-                ((ObservableList) o).removeOnListChangedCallback(breakObjectListOrientedLayeringHandler);
-        }
         super.onDestroyView();
     }
 
     @Override
     public void onExcludedAppsSelected(final List<String> excludedApps) {
         Objects.requireNonNull(binding, "Tried to set excluded apps while no view was loaded");
-        binding.getConfig().getInterfaceSection().setExcludedApplications(Attribute.iterableToString(excludedApps));
+        final ObservableList<String> excludedApplications =
+                binding.getConfig().getInterface().getExcludedApplications();
+        excludedApplications.clear();
+        excludedApplications.addAll(excludedApps);
     }
 
     private void onFinished() {
@@ -195,25 +134,27 @@ public class TunnelEditorFragment extends BaseFragment implements AppExclusionLi
     public boolean onOptionsItemSelected(final MenuItem item) {
         switch (item.getItemId()) {
             case R.id.menu_action_save:
-                final Config newConfig = new Config();
+                if (binding == null)
+                    return false;
+                final Config newConfig;
                 try {
-                    binding.getConfig().commitData(newConfig);
+                    newConfig = binding.getConfig().resolve();
                 } catch (final Exception e) {
                     final String error = ExceptionLoggers.unwrapMessage(e);
-                    final String tunnelName = tunnel == null ? binding.getConfig().getName() : tunnel.getName();
+                    final String tunnelName = tunnel == null ? binding.getName() : tunnel.getName();
                     final String message = getString(R.string.config_save_error, tunnelName, error);
                     Log.e(TAG, message, e);
                     Snackbar.make(binding.mainContainer, error, Snackbar.LENGTH_LONG).show();
                     return false;
                 }
                 if (tunnel == null) {
-                    Log.d(TAG, "Attempting to create new tunnel " + binding.getConfig().getName());
+                    Log.d(TAG, "Attempting to create new tunnel " + binding.getName());
                     final TunnelManager manager = Application.getTunnelManager();
-                    manager.create(binding.getConfig().getName(), newConfig)
+                    manager.create(binding.getName(), newConfig)
                             .whenComplete(this::onTunnelCreated);
-                } else if (!tunnel.getName().equals(binding.getConfig().getName())) {
-                    Log.d(TAG, "Attempting to rename tunnel to " + binding.getConfig().getName());
-                    tunnel.setName(binding.getConfig().getName())
+                } else if (!tunnel.getName().equals(binding.getName())) {
+                    Log.d(TAG, "Attempting to rename tunnel to " + binding.getName());
+                    tunnel.setName(binding.getName())
                             .whenComplete((a, b) -> onTunnelRenamed(tunnel, newConfig, b));
                 } else {
                     Log.d(TAG, "Attempting to save config of " + tunnel.getName());
@@ -229,7 +170,7 @@ public class TunnelEditorFragment extends BaseFragment implements AppExclusionLi
     public void onRequestSetExcludedApplications(@SuppressWarnings("unused") final View view) {
         final FragmentManager fragmentManager = getFragmentManager();
         if (fragmentManager != null && binding != null) {
-            final String[] excludedApps = Attribute.stringToList(binding.getConfig().getInterfaceSection().getExcludedApplications());
+            final ArrayList<String> excludedApps = new ArrayList<>(binding.getConfig().getInterface().getExcludedApplications());
             final AppListDialogFragment fragment = AppListDialogFragment.newInstance(excludedApps, this);
             fragment.show(fragmentManager, null);
         }
@@ -237,19 +178,25 @@ public class TunnelEditorFragment extends BaseFragment implements AppExclusionLi
 
     @Override
     public void onSaveInstanceState(final Bundle outState) {
-        outState.putParcelable(KEY_LOCAL_CONFIG, binding.getConfig());
+        if (binding != null)
+            outState.putParcelable(KEY_LOCAL_CONFIG, binding.getConfig());
         outState.putString(KEY_ORIGINAL_NAME, tunnel == null ? null : tunnel.getName());
         super.onSaveInstanceState(outState);
     }
 
     @Override
-    public void onSelectedTunnelChanged(@Nullable final Tunnel oldTunnel, @Nullable final Tunnel newTunnel) {
+    public void onSelectedTunnelChanged(@Nullable final Tunnel oldTunnel,
+                                        @Nullable final Tunnel newTunnel) {
         tunnel = newTunnel;
         if (binding == null)
             return;
-        binding.setConfig(new Config.Observable(null, null));
-        if (tunnel != null)
-            tunnel.getConfigAsync().thenAccept(a -> onConfigLoaded(tunnel.getName(), a));
+        binding.setConfig(new ConfigProxy());
+        if (tunnel != null) {
+            binding.setName(tunnel.getName());
+            tunnel.getConfigAsync().thenAccept(this::onConfigLoaded);
+        } else {
+            binding.setName("");
+        }
     }
 
     private void onTunnelCreated(final Tunnel newTunnel, @Nullable final Throwable throwable) {
@@ -301,7 +248,7 @@ public class TunnelEditorFragment extends BaseFragment implements AppExclusionLi
             onSelectedTunnelChanged(null, getSelectedTunnel());
         } else {
             tunnel = getSelectedTunnel();
-            final Config.Observable config = savedInstanceState.getParcelable(KEY_LOCAL_CONFIG);
+            final ConfigProxy config = savedInstanceState.getParcelable(KEY_LOCAL_CONFIG);
             final String originalName = savedInstanceState.getString(KEY_ORIGINAL_NAME);
             if (tunnel != null && !tunnel.getName().equals(originalName))
                 onSelectedTunnelChanged(null, tunnel);
diff --git a/app/src/main/java/com/wireguard/android/fragment/TunnelListFragment.java b/app/src/main/java/com/wireguard/android/fragment/TunnelListFragment.java
index 7509e40c..783c0a29 100644
--- a/app/src/main/java/com/wireguard/android/fragment/TunnelListFragment.java
+++ b/app/src/main/java/com/wireguard/android/fragment/TunnelListFragment.java
@@ -41,9 +41,10 @@ import com.wireguard.android.util.ExceptionLoggers;
 import com.wireguard.android.widget.MultiselectableRelativeLayout;
 import com.wireguard.android.widget.fab.FloatingActionsMenuRecyclerViewScrollListener;
 import com.wireguard.config.Config;
+import com.wireguard.config.ParseException;
 
-import java.io.BufferedReader;
-import java.io.InputStreamReader;
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Collection;
@@ -79,13 +80,13 @@ public class TunnelListFragment extends BaseFragment {
     private void importTunnel(@NonNull final String configText) {
         try {
             // Ensure the config text is parseable before proceeding…
-            Config.from(configText);
+            Config.parse(new ByteArrayInputStream(configText.getBytes(StandardCharsets.UTF_8)));
 
             // Config text is valid, now create the tunnel…
             final FragmentManager fragmentManager = getFragmentManager();
             if (fragmentManager != null)
                 ConfigNamingDialogFragment.newInstance(configText).show(fragmentManager, null);
-        } catch (final Exception exception) {
+        } catch (final IllegalArgumentException | IOException | ParseException exception) {
             onTunnelImportFinished(Collections.emptyList(), Collections.singletonList(exception));
         }
     }
@@ -122,7 +123,6 @@ public class TunnelListFragment extends BaseFragment {
 
             if (isZip) {
                 try (ZipInputStream zip = new ZipInputStream(contentResolver.openInputStream(uri))) {
-                    BufferedReader reader = new BufferedReader(new InputStreamReader(zip, StandardCharsets.UTF_8));
                     ZipEntry entry;
                     while ((entry = zip.getNextEntry()) != null) {
                         if (entry.isDirectory())
@@ -140,7 +140,7 @@ public class TunnelListFragment extends BaseFragment {
                             continue;
                         Config config = null;
                         try {
-                            config = Config.from(reader);
+                            config = Config.parse(zip);
                         } catch (Exception e) {
                             throwables.add(e);
                         }
@@ -150,7 +150,7 @@ public class TunnelListFragment extends BaseFragment {
                 }
             } else {
                 futureTunnels.add(Application.getTunnelManager().create(name,
-                        Config.from(contentResolver.openInputStream(uri))).toCompletableFuture());
+                        Config.parse(contentResolver.openInputStream(uri))).toCompletableFuture());
             }
 
             if (futureTunnels.isEmpty()) {
diff --git a/app/src/main/java/com/wireguard/android/model/ApplicationData.java b/app/src/main/java/com/wireguard/android/model/ApplicationData.java
index efe1ef87..f7c335de 100644
--- a/app/src/main/java/com/wireguard/android/model/ApplicationData.java
+++ b/app/src/main/java/com/wireguard/android/model/ApplicationData.java
@@ -13,7 +13,6 @@ import com.wireguard.android.BR;
 import com.wireguard.util.Keyed;
 
 public class ApplicationData extends BaseObservable implements Keyed<String> {
-
     private final Drawable icon;
     private final String name;
     private final String packageName;
diff --git a/app/src/main/java/com/wireguard/android/model/Tunnel.java b/app/src/main/java/com/wireguard/android/model/Tunnel.java
index 6d37e009..9092b288 100644
--- a/app/src/main/java/com/wireguard/android/model/Tunnel.java
+++ b/app/src/main/java/com/wireguard/android/model/Tunnel.java
@@ -49,7 +49,8 @@ public class Tunnel extends BaseObservable implements Keyed<String> {
         return manager.delete(this);
     }
 
-    @Bindable @Nullable
+    @Bindable
+    @Nullable
     public Config getConfig() {
         if (config == null)
             manager.getTunnelConfig(this).whenComplete(ExceptionLoggers.E);
@@ -81,7 +82,8 @@ public class Tunnel extends BaseObservable implements Keyed<String> {
         return TunnelManager.getTunnelState(this);
     }
 
-    @Bindable @Nullable
+    @Bindable
+    @Nullable
     public Statistics getStatistics() {
         // FIXME: Check age of statistics.
         if (statistics == null)
diff --git a/app/src/main/java/com/wireguard/android/model/TunnelManager.java b/app/src/main/java/com/wireguard/android/model/TunnelManager.java
index 3fd7bfc0..83df3595 100644
--- a/app/src/main/java/com/wireguard/android/model/TunnelManager.java
+++ b/app/src/main/java/com/wireguard/android/model/TunnelManager.java
@@ -44,6 +44,7 @@ public final class TunnelManager extends BaseObservable {
     private static final String KEY_LAST_USED_TUNNEL = "last_used_tunnel";
     private static final String KEY_RESTORE_ON_BOOT = "restore_on_boot";
     private static final String KEY_RUNNING_TUNNELS = "enabled_configs";
+
     private final CompletableFuture<ObservableSortedKeyedList<String, Tunnel>> completableTunnels = new CompletableFuture<>();
     private final ConfigStore configStore;
     private final Context context = Application.get();
@@ -111,7 +112,8 @@ public final class TunnelManager extends BaseObservable {
         });
     }
 
-    @Bindable @Nullable
+    @Bindable
+    @Nullable
     public Tunnel getLastUsedTunnel() {
         return lastUsedTunnel;
     }
diff --git a/app/src/main/java/com/wireguard/android/preference/VersionPreference.java b/app/src/main/java/com/wireguard/android/preference/VersionPreference.java
index 228facc7..1f3f5aa8 100644
--- a/app/src/main/java/com/wireguard/android/preference/VersionPreference.java
+++ b/app/src/main/java/com/wireguard/android/preference/VersionPreference.java
@@ -34,7 +34,8 @@ public class VersionPreference extends Preference {
         });
     }
 
-    @Override @Nullable
+    @Nullable
+    @Override
     public CharSequence getSummary() {
         return versionSummary;
     }
diff --git a/app/src/main/java/com/wireguard/android/util/ExceptionLoggers.java b/app/src/main/java/com/wireguard/android/util/ExceptionLoggers.java
index a32e77a4..199b1fbd 100644
--- a/app/src/main/java/com/wireguard/android/util/ExceptionLoggers.java
+++ b/app/src/main/java/com/wireguard/android/util/ExceptionLoggers.java
@@ -5,9 +5,15 @@
 
 package com.wireguard.android.util;
 
+import android.content.res.Resources;
 import android.support.annotation.Nullable;
 import android.util.Log;
 
+import com.wireguard.android.Application;
+import com.wireguard.android.R;
+import com.wireguard.config.ParseException;
+import com.wireguard.crypto.Key;
+
 import java9.util.concurrent.CompletionException;
 import java9.util.function.BiConsumer;
 
@@ -34,12 +40,35 @@ public enum ExceptionLoggers implements BiConsumer<Object, Throwable> {
         return throwable;
     }
 
-    public static String unwrapMessage(Throwable throwable) {
-        throwable = unwrap(throwable);
-        final String message = throwable.getMessage();
-        if (message != null)
-            return message;
-        return throwable.getClass().getSimpleName();
+    public static String unwrapMessage(final Throwable throwable) {
+        final Throwable innerThrowable = unwrap(throwable);
+        final Resources resources = Application.get().getResources();
+        String message;
+        if (innerThrowable instanceof ParseException) {
+            final ParseException parseException = (ParseException) innerThrowable;
+            message = resources.getString(R.string.parse_error, parseException.getText(), parseException.getContext());
+            if (parseException.getMessage() != null)
+                message += ": " + parseException.getMessage();
+        } else if (innerThrowable instanceof Key.KeyFormatException) {
+            final Key.KeyFormatException keyFormatException = (Key.KeyFormatException) innerThrowable;
+            switch (keyFormatException.getFormat()) {
+                case BASE64:
+                    message = resources.getString(R.string.key_length_base64_exception_message);
+                    break;
+                case BINARY:
+                    message = resources.getString(R.string.key_length_exception_message);
+                    break;
+                case HEX:
+                    message = resources.getString(R.string.key_length_hex_exception_message);
+                    break;
+                default:
+                    // Will never happen, as getFormat is not nullable.
+                    message = null;
+            }
+        } else {
+            message = throwable.getMessage();
+        }
+        return message != null ? message : innerThrowable.getClass().getSimpleName();
     }
 
     @Override
diff --git a/app/src/main/java/com/wireguard/android/util/FragmentUtils.java b/app/src/main/java/com/wireguard/android/util/FragmentUtils.java
index d5838a95..b7fdd095 100644
--- a/app/src/main/java/com/wireguard/android/util/FragmentUtils.java
+++ b/app/src/main/java/com/wireguard/android/util/FragmentUtils.java
@@ -11,7 +11,6 @@ import android.view.ContextThemeWrapper;
 import com.wireguard.android.activity.SettingsActivity;
 
 public final class FragmentUtils {
-
     private FragmentUtils() {
         // Prevent instantiation
     }
diff --git a/app/src/main/java/com/wireguard/android/util/ObservableKeyedArrayList.java b/app/src/main/java/com/wireguard/android/util/ObservableKeyedArrayList.java
index 2ba87535..7af829fb 100644
--- a/app/src/main/java/com/wireguard/android/util/ObservableKeyedArrayList.java
+++ b/app/src/main/java/com/wireguard/android/util/ObservableKeyedArrayList.java
@@ -64,13 +64,15 @@ public class ObservableKeyedArrayList<K, E extends Keyed<? extends K>>
         return indexOfKey(key) >= 0;
     }
 
-    @Override @Nullable
+    @Nullable
+    @Override
     public E get(final K key) {
         final int index = indexOfKey(key);
         return index >= 0 ? get(index) : null;
     }
 
-    @Override @Nullable
+    @Nullable
+    @Override
     public E getLast(final K key) {
         final int index = lastIndexOfKey(key);
         return index >= 0 ? get(index) : null;
diff --git a/app/src/main/java/com/wireguard/android/util/ObservableSortedKeyedArrayList.java b/app/src/main/java/com/wireguard/android/util/ObservableSortedKeyedArrayList.java
index 7ef94106..d287d33d 100644
--- a/app/src/main/java/com/wireguard/android/util/ObservableSortedKeyedArrayList.java
+++ b/app/src/main/java/com/wireguard/android/util/ObservableSortedKeyedArrayList.java
@@ -28,8 +28,7 @@ import java.util.Spliterator;
 
 public class ObservableSortedKeyedArrayList<K, E extends Keyed<? extends K>>
         extends ObservableKeyedArrayList<K, E> implements ObservableSortedKeyedList<K, E> {
-    @Nullable
-    private final Comparator<? super K> comparator;
+    @Nullable private final Comparator<? super K> comparator;
     private final transient KeyList<K, E> keyList = new KeyList<>(this);
 
     @SuppressWarnings("WeakerAccess")
diff --git a/app/src/main/java/com/wireguard/android/viewmodel/ConfigProxy.java b/app/src/main/java/com/wireguard/android/viewmodel/ConfigProxy.java
new file mode 100644
index 00000000..abe8cbcf
--- /dev/null
+++ b/app/src/main/java/com/wireguard/android/viewmodel/ConfigProxy.java
@@ -0,0 +1,93 @@
+/*
+ * Copyright © 2017-2018 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.android.viewmodel;
+
+import android.databinding.ObservableArrayList;
+import android.databinding.ObservableList;
+import android.os.Parcel;
+import android.os.Parcelable;
+
+import com.wireguard.config.Config;
+import com.wireguard.config.ParseException;
+import com.wireguard.config.Peer;
+
+import java.util.ArrayList;
+import java.util.Collection;
+
+public class ConfigProxy implements Parcelable {
+    public static final Parcelable.Creator<ConfigProxy> CREATOR = new ConfigProxyCreator();
+
+    private final InterfaceProxy interfaze;
+    private final ObservableList<PeerProxy> peers = new ObservableArrayList<>();
+
+    private ConfigProxy(final Parcel in) {
+        interfaze = in.readParcelable(InterfaceProxy.class.getClassLoader());
+        in.readTypedList(peers, PeerProxy.CREATOR);
+        for (final PeerProxy proxy : peers)
+            proxy.bind(this);
+    }
+
+    public ConfigProxy(final Config other) {
+        interfaze = new InterfaceProxy(other.getInterface());
+        for (final Peer peer : other.getPeers()) {
+            final PeerProxy proxy = new PeerProxy(peer);
+            peers.add(proxy);
+            proxy.bind(this);
+        }
+    }
+
+    public ConfigProxy() {
+        interfaze = new InterfaceProxy();
+    }
+
+    public PeerProxy addPeer() {
+        final PeerProxy proxy = new PeerProxy();
+        peers.add(proxy);
+        proxy.bind(this);
+        return proxy;
+    }
+
+    @Override
+    public int describeContents() {
+        return 0;
+    }
+
+    public InterfaceProxy getInterface() {
+        return interfaze;
+    }
+
+    public ObservableList<PeerProxy> getPeers() {
+        return peers;
+    }
+
+    public Config resolve() throws ParseException {
+        final Collection<Peer> resolvedPeers = new ArrayList<>();
+        for (final PeerProxy proxy : peers)
+            resolvedPeers.add(proxy.resolve());
+        return new Config.Builder()
+                .setInterface(interfaze.resolve())
+                .addPeers(resolvedPeers)
+                .build();
+    }
+
+    @Override
+    public void writeToParcel(final Parcel dest, final int flags) {
+        dest.writeParcelable(interfaze, flags);
+        dest.writeTypedList(peers);
+    }
+
+    private static class ConfigProxyCreator implements Parcelable.Creator<ConfigProxy> {
+        @Override
+        public ConfigProxy createFromParcel(final Parcel in) {
+            return new ConfigProxy(in);
+        }
+
+        @Override
+        public ConfigProxy[] newArray(final int size) {
+            return new ConfigProxy[size];
+        }
+    }
+}
diff --git a/app/src/main/java/com/wireguard/android/viewmodel/InterfaceProxy.java b/app/src/main/java/com/wireguard/android/viewmodel/InterfaceProxy.java
new file mode 100644
index 00000000..63d82042
--- /dev/null
+++ b/app/src/main/java/com/wireguard/android/viewmodel/InterfaceProxy.java
@@ -0,0 +1,189 @@
+/*
+ * Copyright © 2017-2018 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.android.viewmodel;
+
+import android.databinding.BaseObservable;
+import android.databinding.Bindable;
+import android.databinding.ObservableArrayList;
+import android.databinding.ObservableList;
+import android.os.Parcel;
+import android.os.Parcelable;
+
+import com.wireguard.android.BR;
+import com.wireguard.config.Attribute;
+import com.wireguard.config.Interface;
+import com.wireguard.config.ParseException;
+import com.wireguard.crypto.Key;
+import com.wireguard.crypto.KeyPair;
+
+import java.net.InetAddress;
+import java.util.List;
+
+import java9.util.stream.Collectors;
+import java9.util.stream.StreamSupport;
+
+public class InterfaceProxy extends BaseObservable implements Parcelable {
+    public static final Parcelable.Creator<InterfaceProxy> CREATOR = new InterfaceProxyCreator();
+
+    private final ObservableList<String> excludedApplications = new ObservableArrayList<>();
+    private String addresses;
+    private String dnsServers;
+    private String listenPort;
+    private String mtu;
+    private String privateKey;
+    private String publicKey;
+
+    private InterfaceProxy(final Parcel in) {
+        addresses = in.readString();
+        dnsServers = in.readString();
+        in.readStringList(excludedApplications);
+        listenPort = in.readString();
+        mtu = in.readString();
+        privateKey = in.readString();
+        publicKey = in.readString();
+    }
+
+    public InterfaceProxy(final Interface other) {
+        addresses = Attribute.join(other.getAddresses());
+        final List<String> dnsServerStrings = StreamSupport.stream(other.getDnsServers())
+                .map(InetAddress::getHostAddress)
+                .collect(Collectors.toUnmodifiableList());
+        dnsServers = Attribute.join(dnsServerStrings);
+        excludedApplications.addAll(other.getExcludedApplications());
+        listenPort = other.getListenPort().map(String::valueOf).orElse("");
+        mtu = other.getMtu().map(String::valueOf).orElse("");
+        final KeyPair keyPair = other.getKeyPair();
+        privateKey = keyPair.getPrivateKey().toBase64();
+        publicKey = keyPair.getPublicKey().toBase64();
+    }
+
+    public InterfaceProxy() {
+        addresses = "";
+        dnsServers = "";
+        listenPort = "";
+        mtu = "";
+        privateKey = "";
+        publicKey = "";
+    }
+
+    @Override
+    public int describeContents() {
+        return 0;
+    }
+
+    public void generateKeyPair() {
+        final KeyPair keyPair = new KeyPair();
+        privateKey = keyPair.getPrivateKey().toBase64();
+        publicKey = keyPair.getPublicKey().toBase64();
+        notifyPropertyChanged(BR.privateKey);
+        notifyPropertyChanged(BR.publicKey);
+    }
+
+    @Bindable
+    public String getAddresses() {
+        return addresses;
+    }
+
+    @Bindable
+    public String getDnsServers() {
+        return dnsServers;
+    }
+
+    public ObservableList<String> getExcludedApplications() {
+        return excludedApplications;
+    }
+
+    @Bindable
+    public String getListenPort() {
+        return listenPort;
+    }
+
+    @Bindable
+    public String getMtu() {
+        return mtu;
+    }
+
+    @Bindable
+    public String getPrivateKey() {
+        return privateKey;
+    }
+
+    @Bindable
+    public String getPublicKey() {
+        return publicKey;
+    }
+
+    public Interface resolve() throws ParseException {
+        final Interface.Builder builder = new Interface.Builder();
+        if (!addresses.isEmpty())
+            builder.parseAddresses(addresses);
+        if (!dnsServers.isEmpty())
+            builder.parseDnsServers(dnsServers);
+        if (!excludedApplications.isEmpty())
+            builder.excludeApplications(excludedApplications);
+        if (!listenPort.isEmpty())
+            builder.parseListenPort(listenPort);
+        if (!mtu.isEmpty())
+            builder.parseMtu(mtu);
+        if (!privateKey.isEmpty())
+            builder.parsePrivateKey(privateKey);
+        return builder.build();
+    }
+
+    public void setAddresses(final String addresses) {
+        this.addresses = addresses;
+        notifyPropertyChanged(BR.addresses);
+    }
+
+    public void setDnsServers(final String dnsServers) {
+        this.dnsServers = dnsServers;
+        notifyPropertyChanged(BR.dnsServers);
+    }
+
+    public void setListenPort(final String listenPort) {
+        this.listenPort = listenPort;
+        notifyPropertyChanged(BR.listenPort);
+    }
+
+    public void setMtu(final String mtu) {
+        this.mtu = mtu;
+        notifyPropertyChanged(BR.mtu);
+    }
+
+    public void setPrivateKey(final String privateKey) {
+        this.privateKey = privateKey;
+        try {
+            publicKey = new KeyPair(Key.fromBase64(privateKey)).getPublicKey().toBase64();
+        } catch (final Key.KeyFormatException ignored) {
+            publicKey = "";
+        }
+        notifyPropertyChanged(BR.privateKey);
+        notifyPropertyChanged(BR.publicKey);
+    }
+
+    @Override
+    public void writeToParcel(final Parcel dest, final int flags) {
+        dest.writeString(addresses);
+        dest.writeString(dnsServers);
+        dest.writeStringList(excludedApplications);
+        dest.writeString(listenPort);
+        dest.writeString(mtu);
+        dest.writeString(privateKey);
+        dest.writeString(publicKey);
+    }
+
+    private static class InterfaceProxyCreator implements Parcelable.Creator<InterfaceProxy> {
+        @Override
+        public InterfaceProxy createFromParcel(final Parcel in) {
+            return new InterfaceProxy(in);
+        }
+
+        @Override
+        public InterfaceProxy[] newArray(final int size) {
+            return new InterfaceProxy[size];
+        }
+    }
+}
diff --git a/app/src/main/java/com/wireguard/android/viewmodel/PeerProxy.java b/app/src/main/java/com/wireguard/android/viewmodel/PeerProxy.java
new file mode 100644
index 00000000..822a4278
--- /dev/null
+++ b/app/src/main/java/com/wireguard/android/viewmodel/PeerProxy.java
@@ -0,0 +1,379 @@
+/*
+ * Copyright © 2017-2018 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.android.viewmodel;
+
+import android.databinding.BaseObservable;
+import android.databinding.Bindable;
+import android.databinding.Observable;
+import android.databinding.ObservableList;
+import android.os.Parcel;
+import android.os.Parcelable;
+import android.support.annotation.Nullable;
+
+import com.wireguard.android.BR;
+import com.wireguard.config.Attribute;
+import com.wireguard.config.InetEndpoint;
+import com.wireguard.config.ParseException;
+import com.wireguard.config.Peer;
+import com.wireguard.crypto.Key;
+
+import java.lang.ref.WeakReference;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Set;
+
+import java9.util.Lists;
+import java9.util.Sets;
+import java9.util.stream.Collectors;
+import java9.util.stream.Stream;
+
+public class PeerProxy extends BaseObservable implements Parcelable {
+    public static final Parcelable.Creator<PeerProxy> CREATOR = new PeerProxyCreator();
+    private static final Set<String> IPV4_PUBLIC_NETWORKS = new LinkedHashSet<>(Lists.of(
+            "0.0.0.0/5", "8.0.0.0/7", "11.0.0.0/8", "12.0.0.0/6", "16.0.0.0/4", "32.0.0.0/3",
+            "64.0.0.0/2", "128.0.0.0/3", "160.0.0.0/5", "168.0.0.0/6", "172.0.0.0/12",
+            "172.32.0.0/11", "172.64.0.0/10", "172.128.0.0/9", "173.0.0.0/8", "174.0.0.0/7",
+            "176.0.0.0/4", "192.0.0.0/9", "192.128.0.0/11", "192.160.0.0/13", "192.169.0.0/16",
+            "192.170.0.0/15", "192.172.0.0/14", "192.176.0.0/12", "192.192.0.0/10",
+            "193.0.0.0/8", "194.0.0.0/7", "196.0.0.0/6", "200.0.0.0/5", "208.0.0.0/4"
+    ));
+    private static final Set<String> IPV4_WILDCARD = Sets.of("0.0.0.0/0");
+
+    private final List<String> dnsRoutes = new ArrayList<>();
+    private String allowedIps;
+    private AllowedIpsState allowedIpsState = AllowedIpsState.INVALID;
+    private String endpoint;
+    @Nullable private InterfaceDnsListener interfaceDnsListener;
+    @Nullable private ConfigProxy owner;
+    @Nullable private PeerListListener peerListListener;
+    private String persistentKeepalive;
+    private String preSharedKey;
+    private String publicKey;
+    private int totalPeers;
+
+    private PeerProxy(final Parcel in) {
+        allowedIps = in.readString();
+        endpoint = in.readString();
+        persistentKeepalive = in.readString();
+        preSharedKey = in.readString();
+        publicKey = in.readString();
+    }
+
+    public PeerProxy(final Peer other) {
+        allowedIps = Attribute.join(other.getAllowedIps());
+        endpoint = other.getEndpoint().map(InetEndpoint::toString).orElse("");
+        persistentKeepalive = other.getPersistentKeepalive().map(String::valueOf).orElse("");
+        preSharedKey = other.getPreSharedKey().map(Key::toBase64).orElse("");
+        publicKey = other.getPublicKey().toBase64();
+    }
+
+    public PeerProxy() {
+        allowedIps = "";
+        endpoint = "";
+        persistentKeepalive = "";
+        preSharedKey = "";
+        publicKey = "";
+    }
+
+    public void bind(final ConfigProxy owner) {
+        final InterfaceProxy interfaze = owner.getInterface();
+        final ObservableList<PeerProxy> peers = owner.getPeers();
+        if (interfaceDnsListener == null)
+            interfaceDnsListener = new InterfaceDnsListener(this);
+        interfaze.addOnPropertyChangedCallback(interfaceDnsListener);
+        setInterfaceDns(interfaze.getDnsServers());
+        if (peerListListener == null)
+            peerListListener = new PeerListListener(this);
+        peers.addOnListChangedCallback(peerListListener);
+        setTotalPeers(peers.size());
+        this.owner = owner;
+    }
+
+    private void calculateAllowedIpsState() {
+        final AllowedIpsState newState;
+        if (totalPeers == 1) {
+            // String comparison works because we only care if allowedIps is a superset of one of
+            // the above sets of (valid) *networks*. We are not checking for a superset based on
+            // the individual addresses in each set.
+            final Collection<String> networkStrings = getAllowedIpsSet();
+            // If allowedIps contains both the wildcard and the public networks, then private
+            // networks aren't excluded!
+            if (networkStrings.containsAll(IPV4_WILDCARD))
+                newState = AllowedIpsState.CONTAINS_IPV4_WILDCARD;
+            else if (networkStrings.containsAll(IPV4_PUBLIC_NETWORKS))
+                newState = AllowedIpsState.CONTAINS_IPV4_PUBLIC_NETWORKS;
+            else
+                newState = AllowedIpsState.OTHER;
+        } else {
+            newState = AllowedIpsState.INVALID;
+        }
+        if (newState != allowedIpsState) {
+            allowedIpsState = newState;
+            notifyPropertyChanged(BR.ableToExcludePrivateIps);
+            notifyPropertyChanged(BR.excludingPrivateIps);
+        }
+    }
+
+    @Override
+    public int describeContents() {
+        return 0;
+    }
+
+    @Bindable
+    public String getAllowedIps() {
+        return allowedIps;
+    }
+
+    private Set<String> getAllowedIpsSet() {
+        return new LinkedHashSet<>(Lists.of(Attribute.split(allowedIps)));
+    }
+
+    @Bindable
+    public String getEndpoint() {
+        return endpoint;
+    }
+
+    @Bindable
+    public String getPersistentKeepalive() {
+        return persistentKeepalive;
+    }
+
+    @Bindable
+    public String getPreSharedKey() {
+        return preSharedKey;
+    }
+
+    @Bindable
+    public String getPublicKey() {
+        return publicKey;
+    }
+
+    @Bindable
+    public boolean isAbleToExcludePrivateIps() {
+        return allowedIpsState == AllowedIpsState.CONTAINS_IPV4_PUBLIC_NETWORKS
+                || allowedIpsState == AllowedIpsState.CONTAINS_IPV4_WILDCARD;
+    }
+
+    @Bindable
+    public boolean isExcludingPrivateIps() {
+        return allowedIpsState == AllowedIpsState.CONTAINS_IPV4_PUBLIC_NETWORKS;
+    }
+
+    public Peer resolve() throws ParseException {
+        final Peer.Builder builder = new Peer.Builder();
+        if (!allowedIps.isEmpty())
+            builder.parseAllowedIPs(allowedIps);
+        if (!endpoint.isEmpty())
+            builder.parseEndpoint(endpoint);
+        if (!persistentKeepalive.isEmpty())
+            builder.parsePersistentKeepalive(persistentKeepalive);
+        if (!preSharedKey.isEmpty())
+            builder.parsePreSharedKey(preSharedKey);
+        if (!publicKey.isEmpty())
+            builder.parsePublicKey(publicKey);
+        return builder.build();
+    }
+
+    public void setAllowedIps(final String allowedIps) {
+        this.allowedIps = allowedIps;
+        notifyPropertyChanged(BR.allowedIps);
+        calculateAllowedIpsState();
+    }
+
+    public void setEndpoint(final String endpoint) {
+        this.endpoint = endpoint;
+        notifyPropertyChanged(BR.endpoint);
+    }
+
+    public void setExcludingPrivateIps(final boolean excludingPrivateIps) {
+        if (!isAbleToExcludePrivateIps() || isExcludingPrivateIps() == excludingPrivateIps)
+            return;
+        final Set<String> oldNetworks = excludingPrivateIps ? IPV4_WILDCARD : IPV4_PUBLIC_NETWORKS;
+        final Set<String> newNetworks = excludingPrivateIps ? IPV4_PUBLIC_NETWORKS : IPV4_WILDCARD;
+        final Collection<String> input = getAllowedIpsSet();
+        final int outputSize = input.size() - oldNetworks.size() + newNetworks.size();
+        final Collection<String> output = new LinkedHashSet<>(outputSize);
+        boolean replaced = false;
+        // Replace the first instance of the wildcard with the public network list, or vice versa.
+        for (final String network : input) {
+            if (oldNetworks.contains(network)) {
+                if (!replaced) {
+                    for (final String replacement : newNetworks)
+                        if (!output.contains(replacement))
+                            output.add(replacement);
+                    replaced = true;
+                }
+            } else if (!output.contains(network)) {
+                output.add(network);
+            }
+        }
+        // DNS servers only need to handled specially when we're excluding private IPs.
+        if (excludingPrivateIps)
+            output.addAll(dnsRoutes);
+        else
+            output.removeAll(dnsRoutes);
+        allowedIps = Attribute.join(output);
+        allowedIpsState = excludingPrivateIps ?
+                AllowedIpsState.CONTAINS_IPV4_PUBLIC_NETWORKS : AllowedIpsState.CONTAINS_IPV4_WILDCARD;
+        notifyPropertyChanged(BR.allowedIps);
+        notifyPropertyChanged(BR.excludingPrivateIps);
+    }
+
+    private void setInterfaceDns(final CharSequence dnsServers) {
+        final List<String> newDnsRoutes = Stream.of(Attribute.split(dnsServers))
+                .map(server -> server + "/32")
+                .collect(Collectors.toUnmodifiableList());
+        if (allowedIpsState == AllowedIpsState.CONTAINS_IPV4_PUBLIC_NETWORKS) {
+            final Collection<String> input = getAllowedIpsSet();
+            final Collection<String> output = new LinkedHashSet<>(input.size() + 1);
+            // Yes, this is quadratic in the number of DNS servers, but most users have 1 or 2.
+            for (final String network : input)
+                if (!dnsRoutes.contains(network) || newDnsRoutes.contains(network))
+                    output.add(network);
+            // Since output is a Set, this does the Right Thing™ (it does not duplicate networks).
+            output.addAll(newDnsRoutes);
+            // None of the public networks are /32s, so this cannot change the AllowedIPs state.
+            allowedIps = Attribute.join(output);
+            notifyPropertyChanged(BR.allowedIps);
+        }
+        dnsRoutes.clear();
+        dnsRoutes.addAll(newDnsRoutes);
+    }
+
+    public void setPersistentKeepalive(final String persistentKeepalive) {
+        this.persistentKeepalive = persistentKeepalive;
+        notifyPropertyChanged(BR.persistentKeepalive);
+    }
+
+    public void setPreSharedKey(final String preSharedKey) {
+        this.preSharedKey = preSharedKey;
+        notifyPropertyChanged(BR.preSharedKey);
+    }
+
+    public void setPublicKey(final String publicKey) {
+        this.publicKey = publicKey;
+        notifyPropertyChanged(BR.publicKey);
+    }
+
+    private void setTotalPeers(final int totalPeers) {
+        if (this.totalPeers == totalPeers)
+            return;
+        this.totalPeers = totalPeers;
+        calculateAllowedIpsState();
+    }
+
+    public void unbind() {
+        if (owner == null)
+            return;
+        final InterfaceProxy interfaze = owner.getInterface();
+        final ObservableList<PeerProxy> peers = owner.getPeers();
+        if (interfaceDnsListener != null)
+            interfaze.removeOnPropertyChangedCallback(interfaceDnsListener);
+        if (peerListListener != null)
+            peers.removeOnListChangedCallback(peerListListener);
+        peers.remove(this);
+        setInterfaceDns("");
+        setTotalPeers(0);
+        owner = null;
+    }
+
+    @Override
+    public void writeToParcel(final Parcel dest, final int flags) {
+        dest.writeString(allowedIps);
+        dest.writeString(endpoint);
+        dest.writeString(persistentKeepalive);
+        dest.writeString(preSharedKey);
+        dest.writeString(publicKey);
+    }
+
+    private enum AllowedIpsState {
+        CONTAINS_IPV4_PUBLIC_NETWORKS,
+        CONTAINS_IPV4_WILDCARD,
+        INVALID,
+        OTHER
+    }
+
+    private static final class InterfaceDnsListener extends Observable.OnPropertyChangedCallback {
+        private final WeakReference<PeerProxy> weakPeerProxy;
+
+        private InterfaceDnsListener(final PeerProxy peerProxy) {
+            weakPeerProxy = new WeakReference<>(peerProxy);
+        }
+
+        @Override
+        public void onPropertyChanged(final Observable sender, final int propertyId) {
+            @Nullable final PeerProxy peerProxy = weakPeerProxy.get();
+            if (peerProxy == null) {
+                sender.removeOnPropertyChangedCallback(this);
+                return;
+            }
+            // This shouldn't be possible, but try to avoid a ClassCastException anyway.
+            if (!(sender instanceof InterfaceProxy))
+                return;
+            if (!(propertyId == BR._all || propertyId == BR.dnsServers))
+                return;
+            peerProxy.setInterfaceDns(((InterfaceProxy) sender).getDnsServers());
+        }
+    }
+
+    private static final class PeerListListener
+            extends ObservableList.OnListChangedCallback<ObservableList<PeerProxy>> {
+        private final WeakReference<PeerProxy> weakPeerProxy;
+
+        private PeerListListener(final PeerProxy peerProxy) {
+            weakPeerProxy = new WeakReference<>(peerProxy);
+        }
+
+        @Override
+        public void onChanged(final ObservableList<PeerProxy> sender) {
+            @Nullable final PeerProxy peerProxy = weakPeerProxy.get();
+            if (peerProxy == null) {
+                sender.removeOnListChangedCallback(this);
+                return;
+            }
+            peerProxy.setTotalPeers(sender.size());
+        }
+
+        @Override
+        public void onItemRangeChanged(final ObservableList<PeerProxy> sender,
+                                       final int positionStart, final int itemCount) {
+            // Do nothing.
+        }
+
+        @Override
+        public void onItemRangeInserted(final ObservableList<PeerProxy> sender,
+                                        final int positionStart, final int itemCount) {
+            onChanged(sender);
+        }
+
+        @Override
+        public void onItemRangeMoved(final ObservableList<PeerProxy> sender,
+                                     final int fromPosition, final int toPosition,
+                                     final int itemCount) {
+            // Do nothing.
+        }
+
+        @Override
+        public void onItemRangeRemoved(final ObservableList<PeerProxy> sender,
+                                       final int positionStart, final int itemCount) {
+            onChanged(sender);
+        }
+    }
+
+    private static class PeerProxyCreator implements Parcelable.Creator<PeerProxy> {
+        @Override
+        public PeerProxy createFromParcel(final Parcel in) {
+            return new PeerProxy(in);
+        }
+
+        @Override
+        public PeerProxy[] newArray(final int size) {
+            return new PeerProxy[size];
+        }
+    }
+}
diff --git a/app/src/main/java/com/wireguard/android/widget/KeyInputFilter.java b/app/src/main/java/com/wireguard/android/widget/KeyInputFilter.java
index b6cdada7..6332b856 100644
--- a/app/src/main/java/com/wireguard/android/widget/KeyInputFilter.java
+++ b/app/src/main/java/com/wireguard/android/widget/KeyInputFilter.java
@@ -10,7 +10,7 @@ import android.text.InputFilter;
 import android.text.SpannableStringBuilder;
 import android.text.Spanned;
 
-import com.wireguard.crypto.KeyEncoding;
+import com.wireguard.crypto.Key;
 
 /**
  * InputFilter for entering WireGuard private/public keys encoded with base64.
@@ -25,7 +25,8 @@ public class KeyInputFilter implements InputFilter {
         return new KeyInputFilter();
     }
 
-    @Override @Nullable
+    @Nullable
+    @Override
     public CharSequence filter(final CharSequence source,
                                final int sStart, final int sEnd,
                                final Spanned dest,
@@ -38,9 +39,9 @@ public class KeyInputFilter implements InputFilter {
             final int dIndex = dStart + (sIndex - sStart);
             // Restrict characters to the base64 character set.
             // Ensure adding this character does not push the length over the limit.
-            if (((dIndex + 1 < KeyEncoding.KEY_LENGTH_BASE64 && isAllowed(c)) ||
-                    (dIndex + 1 == KeyEncoding.KEY_LENGTH_BASE64 && c == '=')) &&
-                    dLength + (sIndex - sStart) < KeyEncoding.KEY_LENGTH_BASE64) {
+            if (((dIndex + 1 < Key.Format.BASE64.getLength() && isAllowed(c)) ||
+                    (dIndex + 1 == Key.Format.BASE64.getLength() && c == '=')) &&
+                    dLength + (sIndex - sStart) < Key.Format.BASE64.getLength()) {
                 ++rIndex;
             } else {
                 if (replacement == null)
diff --git a/app/src/main/java/com/wireguard/android/widget/NameInputFilter.java b/app/src/main/java/com/wireguard/android/widget/NameInputFilter.java
index db5336d0..2352630e 100644
--- a/app/src/main/java/com/wireguard/android/widget/NameInputFilter.java
+++ b/app/src/main/java/com/wireguard/android/widget/NameInputFilter.java
@@ -25,7 +25,8 @@ public class NameInputFilter implements InputFilter {
         return new NameInputFilter();
     }
 
-    @Override @Nullable
+    @Nullable
+    @Override
     public CharSequence filter(final CharSequence source,
                                final int sStart, final int sEnd,
                                final Spanned dest,
diff --git a/app/src/main/java/com/wireguard/android/widget/fab/FloatingActionsMenu.java b/app/src/main/java/com/wireguard/android/widget/fab/FloatingActionsMenu.java
index ed838914..7f5b67e6 100644
--- a/app/src/main/java/com/wireguard/android/widget/fab/FloatingActionsMenu.java
+++ b/app/src/main/java/com/wireguard/android/widget/fab/FloatingActionsMenu.java
@@ -539,7 +539,7 @@ public class FloatingActionsMenu extends ViewGroup {
                 return new SavedState[size];
             }
         };
-        public boolean mExpanded;
+        private boolean mExpanded;
 
         public SavedState(final Parcelable parcel) {
             super(parcel);
diff --git a/app/src/main/java/com/wireguard/config/Attribute.java b/app/src/main/java/com/wireguard/config/Attribute.java
index d4bdb6c8..d61cc744 100644
--- a/app/src/main/java/com/wireguard/config/Attribute.java
+++ b/app/src/main/java/com/wireguard/config/Attribute.java
@@ -1,94 +1,49 @@
 /*
- * Copyright © 2017-2018 WireGuard LLC. All Rights Reserved.
+ * Copyright © 2018 WireGuard LLC. All Rights Reserved.
  * SPDX-License-Identifier: Apache-2.0
  */
 
 package com.wireguard.config;
 
-import android.annotation.SuppressLint;
-import android.support.annotation.Nullable;
 import android.text.TextUtils;
 
-import java.util.HashMap;
-import java.util.Map;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
-/**
- * The set of valid attributes for an interface or peer in a WireGuard configuration file.
- */
-
-public enum Attribute {
-    ADDRESS("Address"),
-    ALLOWED_IPS("AllowedIPs"),
-    DNS("DNS"),
-    EXCLUDED_APPLICATIONS("ExcludedApplications"),
-    ENDPOINT("Endpoint"),
-    LISTEN_PORT("ListenPort"),
-    MTU("MTU"),
-    PERSISTENT_KEEPALIVE("PersistentKeepalive"),
-    PRESHARED_KEY("PresharedKey"),
-    PRIVATE_KEY("PrivateKey"),
-    PUBLIC_KEY("PublicKey");
-
-    private static final String[] EMPTY_LIST = new String[0];
-    private static final Map<String, Attribute> KEY_MAP;
-    private static final Pattern LIST_SEPARATOR_PATTERN = Pattern.compile("\\s*,\\s*");
-    private static final Pattern SEPARATOR_PATTERN = Pattern.compile("\\s|=");
-
-    static {
-        KEY_MAP = new HashMap<>(Attribute.values().length);
-        for (final Attribute key : Attribute.values()) {
-            KEY_MAP.put(key.token.toLowerCase(), key);
-        }
-    }
+import java9.util.Optional;
 
-    private final Pattern pattern;
-    private final String token;
+public final class Attribute {
+    private static final Pattern LINE_PATTERN = Pattern.compile("(\\w+)\\s*=\\s*([^\\s#][^#]*)");
+    private static final Pattern LIST_SEPARATOR = Pattern.compile("\\s*,\\s*");
 
-    Attribute(final String token) {
-        pattern = Pattern.compile(token + "\\s*=\\s*(\\S.*)");
-        this.token = token;
-    }
-
-    public static <T> String iterableToString(final Iterable<T> iterable) {
-        return TextUtils.join(", ", iterable);
-    }
-
-    @Nullable
-    public static Attribute match(final CharSequence line) {
-        return KEY_MAP.get(SEPARATOR_PATTERN.split(line)[0].toLowerCase());
-    }
+    private final String key;
+    private final String value;
 
-    public static String[] stringToList(@Nullable final String string) {
-        if (TextUtils.isEmpty(string))
-            return EMPTY_LIST;
-        return LIST_SEPARATOR_PATTERN.split(string.trim());
+    private Attribute(final String key, final String value) {
+        this.key = key;
+        this.value = value;
     }
 
-    @SuppressLint("DefaultLocale")
-    public String composeWith(@Nullable final Object value) {
-        return String.format("%s = %s%n", token, value);
+    public static String join(final Iterable<?> values) {
+        return TextUtils.join(", ", values);
     }
 
-    @SuppressLint("DefaultLocale")
-    public String composeWith(final int value) {
-        return String.format("%s = %d%n", token, value);
+    public static Optional<Attribute> parse(final CharSequence line) {
+        final Matcher matcher = LINE_PATTERN.matcher(line);
+        if (!matcher.matches())
+            return Optional.empty();
+        return Optional.of(new Attribute(matcher.group(1), matcher.group(2)));
     }
 
-    public <T> String composeWith(final Iterable<T> value) {
-        return String.format("%s = %s%n", token, iterableToString(value));
+    public static String[] split(final CharSequence value) {
+        return LIST_SEPARATOR.split(value);
     }
 
-    @Nullable
-    public String parse(final CharSequence line) {
-        final Matcher matcher = pattern.matcher(line);
-        return matcher.matches() ? matcher.group(1) : null;
+    public String getKey() {
+        return key;
     }
 
-    @Nullable
-    public String[] parseList(final CharSequence line) {
-        final Matcher matcher = pattern.matcher(line);
-        return matcher.matches() ? stringToList(matcher.group(1)) : null;
+    public String getValue() {
+        return value;
     }
 }
diff --git a/app/src/main/java/com/wireguard/config/Config.java b/app/src/main/java/com/wireguard/config/Config.java
index 61e31838..7645583d 100644
--- a/app/src/main/java/com/wireguard/config/Config.java
+++ b/app/src/main/java/com/wireguard/config/Config.java
@@ -5,170 +5,193 @@
 
 package com.wireguard.config;
 
-import android.content.Context;
-import android.databinding.BaseObservable;
-import android.databinding.Bindable;
-import android.databinding.ObservableArrayList;
-import android.databinding.ObservableList;
-import android.os.Parcel;
-import android.os.Parcelable;
 import android.support.annotation.Nullable;
 
-import com.android.databinding.library.baseAdapters.BR;
-import com.wireguard.android.Application;
-import com.wireguard.android.R;
-
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
-import java.io.StringReader;
-import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Objects;
+import java.util.Set;
 
 /**
- * Represents a wg-quick configuration file, its name, and its connection state.
+ * Represents the contents of a wg-quick configuration file, made up of one or more "Interface"
+ * sections (combined together), and zero or more "Peer" sections (treated individually).
+ * <p>
+ * Instances of this class are immutable.
  */
-
-public class Config {
-    private final Interface interfaceSection = new Interface();
-    private List<Peer> peers = new ArrayList<>();
-
-    public static Config from(final String string) throws IOException {
-        return from(new BufferedReader(new StringReader(string)));
+public final class Config {
+    private final Interface interfaze;
+    private final List<Peer> peers;
+
+    private Config(final Builder builder) {
+        interfaze = Objects.requireNonNull(builder.interfaze, "An [Interface] section is required");
+        // Defensively copy to ensure immutability even if the Builder is reused.
+        peers = Collections.unmodifiableList(new ArrayList<>(builder.peers));
     }
 
-    public static Config from(final InputStream stream) throws IOException {
-        return from(new BufferedReader(new InputStreamReader(stream, StandardCharsets.UTF_8)));
-    }
-
-    public static Config from(final BufferedReader reader) throws IOException {
-        final Config config = new Config();
-        final Context context = Application.get();
-        Peer currentPeer = null;
-        String line;
-        boolean inInterfaceSection = false;
-        while ((line = reader.readLine()) != null) {
-            final int commentIndex = line.indexOf('#');
-            if (commentIndex != -1)
-                line = line.substring(0, commentIndex);
-            line = line.trim();
-            if (line.isEmpty())
-                continue;
-            if ("[Interface]".toLowerCase().equals(line.toLowerCase())) {
-                currentPeer = null;
-                inInterfaceSection = true;
-            } else if ("[Peer]".toLowerCase().equals(line.toLowerCase())) {
-                currentPeer = new Peer();
-                config.peers.add(currentPeer);
-                inInterfaceSection = false;
-            } else if (inInterfaceSection) {
-                config.interfaceSection.parse(line);
-            } else if (currentPeer != null) {
-                currentPeer.parse(line);
-            } else {
-                throw new IllegalArgumentException(context.getString(R.string.tunnel_error_invalid_config_line, line));
+    /**
+     * Parses an series of "Interface" and "Peer" sections into a {@code Config}. Throws
+     * {@link ParseException} if the input is not well-formed or contains unparseable sections.
+     *
+     * @param stream a stream of UTF-8 text that is interpreted as a WireGuard configuration file
+     * @return a {@code Config} instance representing the supplied configuration
+     */
+    public static Config parse(final InputStream stream) throws IOException, ParseException {
+        final Builder builder = new Builder();
+        try (final BufferedReader reader = new BufferedReader(new InputStreamReader(stream))) {
+            final Collection<String> interfaceLines = new ArrayList<>();
+            final Collection<String> peerLines = new ArrayList<>();
+            boolean inInterfaceSection = false;
+            boolean inPeerSection = false;
+            @Nullable String line;
+            while ((line = reader.readLine()) != null) {
+                final int commentIndex = line.indexOf('#');
+                if (commentIndex != -1)
+                    line = line.substring(0, commentIndex);
+                line = line.trim();
+                if (line.isEmpty())
+                    continue;
+                if (line.startsWith("[")) {
+                    // Consume all [Peer] lines read so far.
+                    if (inPeerSection) {
+                        builder.parsePeer(peerLines);
+                        peerLines.clear();
+                    }
+                    if ("[Interface]".equalsIgnoreCase(line)) {
+                        inInterfaceSection = true;
+                        inPeerSection = false;
+                    } else if ("[Peer]".equalsIgnoreCase(line)) {
+                        inInterfaceSection = false;
+                        inPeerSection = true;
+                    } else {
+                        throw new ParseException("top level", line, "Unknown section name");
+                    }
+                } else if (inInterfaceSection) {
+                    interfaceLines.add(line);
+                } else if (inPeerSection) {
+                    peerLines.add(line);
+                } else {
+                    throw new ParseException("top level", line, "Expected [Interface] or [Peer]");
+                }
             }
+            if (inPeerSection)
+                builder.parsePeer(peerLines);
+            else if (!inInterfaceSection)
+                throw new ParseException("top level", "", "Empty configuration");
+            // Combine all [Interface] sections in the file.
+            builder.parseInterface(interfaceLines);
         }
-        if (!inInterfaceSection && currentPeer == null) {
-            throw new IllegalArgumentException(context.getString(R.string.tunnel_error_no_config_information));
-        }
-        return config;
+        return builder.build();
     }
 
+    @Override
+    public boolean equals(final Object obj) {
+        if (!(obj instanceof Config))
+            return false;
+        final Config other = (Config) obj;
+        return interfaze.equals(other.interfaze) && peers.equals(other.peers);
+    }
+
+    /**
+     * Returns the interface section of the configuration.
+     *
+     * @return the interface configuration
+     */
     public Interface getInterface() {
-        return interfaceSection;
+        return interfaze;
     }
 
+    /**
+     * Returns a list of the configuration's peer sections.
+     *
+     * @return a list of {@link Peer}s
+     */
     public List<Peer> getPeers() {
         return peers;
     }
 
     @Override
+    public int hashCode() {
+        return 31 * interfaze.hashCode() + peers.hashCode();
+    }
+
+    /**
+     * Converts the {@code Config} into a string suitable for debugging purposes. The {@code Config}
+     * is identified by its interface's public key and the number of peers it has.
+     *
+     * @return a concise single-line identifier for the {@code Config}
+     */
+    @Override
     public String toString() {
-        final StringBuilder sb = new StringBuilder().append(interfaceSection);
+        return "(Config " + interfaze + " (" + peers.size() + " peers))";
+    }
+
+    /**
+     * Converts the {@code Config} into a string suitable for use as a {@code wg-quick}
+     * configuration file.
+     *
+     * @return the {@code Config} represented as one [Interface] and zero or more [Peer] sections
+     */
+    public String toWgQuickString() {
+        final StringBuilder sb = new StringBuilder();
+        sb.append("[Interface]\n").append(interfaze.toWgQuickString());
         for (final Peer peer : peers)
-            sb.append('\n').append(peer);
+            sb.append("\n[Peer]\n").append(peer.toWgQuickString());
         return sb.toString();
     }
 
-    public static class Observable extends BaseObservable implements Parcelable {
-        public static final Creator<Observable> CREATOR = new Creator<Observable>() {
-            @Override
-            public Observable createFromParcel(final Parcel in) {
-                return new Observable(in);
-            }
-
-            @Override
-            public Observable[] newArray(final int size) {
-                return new Observable[size];
-            }
-        };
-        private final Interface.Observable observableInterface;
-        private final ObservableList<Peer.Observable> observablePeers;
-        @Nullable private String name;
-
-        public Observable(@Nullable final Config parent, @Nullable final String name) {
-            this.name = name;
-
-            observableInterface = new Interface.Observable(parent == null ? null : parent.interfaceSection);
-            observablePeers = new ObservableArrayList<>();
-            if (parent != null) {
-                for (final Peer peer : parent.getPeers())
-                    observablePeers.add(new Peer.Observable(peer));
-            }
-        }
-
-        private Observable(final Parcel in) {
-            name = in.readString();
-            observableInterface = in.readParcelable(Interface.Observable.class.getClassLoader());
-            observablePeers = new ObservableArrayList<>();
-            in.readTypedList(observablePeers, Peer.Observable.CREATOR);
-        }
+    /**
+     * Serializes the {@code Config} for use with the WireGuard cross-platform userspace API.
+     *
+     * @return the {@code Config} represented as a series of "key=value" lines
+     */
+    public String toWgUserspaceString() {
+        final StringBuilder sb = new StringBuilder();
+        sb.append(interfaze.toWgUserspaceString());
+        sb.append("replace_peers=true\n");
+        for (final Peer peer : peers)
+            sb.append(peer.toWgUserspaceString());
+        return sb.toString();
+    }
 
-        public void commitData(final Config parent) {
-            observableInterface.commitData(parent.interfaceSection);
-            final List<Peer> newPeers = new ArrayList<>(observablePeers.size());
-            for (final Peer.Observable observablePeer : observablePeers) {
-                final Peer peer = new Peer();
-                observablePeer.commitData(peer);
-                newPeers.add(peer);
-            }
-            parent.peers = newPeers;
-            notifyChange();
-        }
+    @SuppressWarnings("UnusedReturnValue")
+    public static final class Builder {
+        // Defaults to an empty set.
+        private final Set<Peer> peers = new LinkedHashSet<>();
+        // No default; must be provided before building.
+        @Nullable private Interface interfaze;
 
-        @Override
-        public int describeContents() {
-            return 0;
+        public Builder addPeer(final Peer peer) {
+            peers.add(peer);
+            return this;
         }
 
-        @Bindable
-        public Interface.Observable getInterfaceSection() {
-            return observableInterface;
+        public Builder addPeers(final Collection<Peer> peers) {
+            this.peers.addAll(peers);
+            return this;
         }
 
-        @Bindable
-        public String getName() {
-            return name == null ? "" : name;
+        public Config build() {
+            return new Config(this);
         }
 
-        @Bindable
-        public ObservableList<Peer.Observable> getPeers() {
-            return observablePeers;
+        public Builder parseInterface(final Iterable<? extends CharSequence> lines) throws ParseException {
+            return setInterface(Interface.parse(lines));
         }
 
-        public void setName(final String name) {
-            this.name = name;
-            notifyPropertyChanged(BR.name);
+        public Builder parsePeer(final Iterable<? extends CharSequence> lines) throws ParseException {
+            return addPeer(Peer.parse(lines));
         }
 
-        @Override
-        public void writeToParcel(final Parcel dest, final int flags) {
-            dest.writeString(name);
-            dest.writeParcelable(observableInterface, flags);
-            dest.writeTypedList(observablePeers);
+        public Builder setInterface(final Interface interfaze) {
+            this.interfaze = interfaze;
+            return this;
         }
     }
 }
diff --git a/app/src/main/java/com/wireguard/config/InetAddresses.java b/app/src/main/java/com/wireguard/config/InetAddresses.java
index c50c5a0e..989598da 100644
--- a/app/src/main/java/com/wireguard/config/InetAddresses.java
+++ b/app/src/main/java/com/wireguard/config/InetAddresses.java
@@ -5,21 +5,22 @@
 
 package com.wireguard.config;
 
-import android.support.annotation.Nullable;
-
-import com.wireguard.android.Application;
-import com.wireguard.android.R;
-
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
+import java.net.Inet4Address;
+import java.net.Inet6Address;
 import java.net.InetAddress;
 
+/**
+ * Utility methods for creating instances of {@link InetAddress}.
+ */
 public final class InetAddresses {
     private static final Method PARSER_METHOD;
 
     static {
         try {
             // This method is only present on Android.
+            // noinspection JavaReflectionMemberAccess
             PARSER_METHOD = InetAddress.class.getMethod("parseNumericAddress", String.class);
         } catch (final NoSuchMethodException e) {
             throw new RuntimeException(e);
@@ -30,13 +31,23 @@ public final class InetAddresses {
         // Prevent instantiation.
     }
 
-    public static InetAddress parse(@Nullable final String address) {
-        if (address == null || address.isEmpty())
-            throw new IllegalArgumentException(Application.get().getString(R.string.tunnel_error_empty_inetaddress));
+    /**
+     * Parses a numeric IPv4 or IPv6 address without performing any DNS lookups.
+     *
+     * @param address a string representing the IP address
+     * @return an instance of {@link Inet4Address} or {@link Inet6Address}, as appropriate
+     */
+    public static InetAddress parse(final String address) {
+        if (address.isEmpty())
+            throw new IllegalArgumentException("Empty address");
         try {
             return (InetAddress) PARSER_METHOD.invoke(null, address);
         } catch (final IllegalAccessException | InvocationTargetException e) {
-            throw new RuntimeException(e.getCause() == null ? e : e.getCause());
+            final Throwable cause = e.getCause();
+            // Re-throw parsing exceptions with the original type, as callers might try to catch
+            // them. On the other hand, callers cannot be expected to handle reflection failures.
+            throw cause instanceof IllegalArgumentException ?
+                    (IllegalArgumentException) cause : new RuntimeException(e);
         }
     }
 }
diff --git a/app/src/main/java/com/wireguard/config/InetEndpoint.java b/app/src/main/java/com/wireguard/config/InetEndpoint.java
index 3efe4203..06d0ca80 100644
--- a/app/src/main/java/com/wireguard/config/InetEndpoint.java
+++ b/app/src/main/java/com/wireguard/config/InetEndpoint.java
@@ -5,36 +5,68 @@
 
 package com.wireguard.config;
 
-import android.annotation.SuppressLint;
+import android.support.annotation.Nullable;
 
-import com.wireguard.android.Application;
-import com.wireguard.android.R;
+import org.threeten.bp.Duration;
+import org.threeten.bp.Instant;
 
 import java.net.Inet4Address;
-import java.net.Inet6Address;
 import java.net.InetAddress;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.net.UnknownHostException;
+import java.util.regex.Pattern;
 
-import javax.annotation.Nullable;
+import java9.util.Optional;
+
+
+/**
+ * An external endpoint (host and port) used to connect to a WireGuard {@link Peer}.
+ * <p>
+ * Instances of this class are externally immutable.
+ */
+public final class InetEndpoint {
+    private static final Pattern BARE_IPV6 = Pattern.compile("^[^\\[]*:");
+    private static final Pattern FORBIDDEN_CHARACTERS = Pattern.compile("[/?#]");
 
-public class InetEndpoint {
     private final String host;
+    private final boolean isResolved;
+    private final Object lock = new Object();
     private final int port;
-    @Nullable private InetAddress resolvedHost;
+    private Instant lastResolution = Instant.EPOCH;
+    @Nullable private InetEndpoint resolved;
 
-    public InetEndpoint(@Nullable final String endpoint) {
-        if (endpoint.indexOf('/') != -1 || endpoint.indexOf('?') != -1 || endpoint.indexOf('#') != -1)
-            throw new IllegalArgumentException(Application.get().getString(R.string.tunnel_error_forbidden_endpoint_chars));
+    private InetEndpoint(final String host, final boolean isResolved, final int port) {
+        this.host = host;
+        this.isResolved = isResolved;
+        this.port = port;
+    }
+
+    public static InetEndpoint parse(final String endpoint) {
+        if (FORBIDDEN_CHARACTERS.matcher(endpoint).find())
+            throw new IllegalArgumentException("Forbidden characters in Endpoint");
         final URI uri;
         try {
             uri = new URI("wg://" + endpoint);
         } catch (final URISyntaxException e) {
             throw new IllegalArgumentException(e);
         }
-        host = uri.getHost();
-        port = uri.getPort();
+        try {
+            InetAddresses.parse(uri.getHost());
+            // Parsing ths host as a numeric address worked, so we don't need to do DNS lookups.
+            return new InetEndpoint(uri.getHost(), true, uri.getPort());
+        } catch (final IllegalArgumentException ignored) {
+            // Failed to parse the host as a numeric address, so it must be a DNS hostname/FQDN.
+            return new InetEndpoint(uri.getHost(), false, uri.getPort());
+        }
+    }
+
+    @Override
+    public boolean equals(final Object obj) {
+        if (!(obj instanceof InetEndpoint))
+            return false;
+        final InetEndpoint other = (InetEndpoint) obj;
+        return host.equals(other.host) && port == other.port;
     }
 
     public String getHost() {
@@ -45,28 +77,47 @@ public class InetEndpoint {
         return port;
     }
 
-    @SuppressLint("DefaultLocale")
-    public String getResolvedEndpoint() throws UnknownHostException {
-        if (resolvedHost == null) {
-            final InetAddress[] candidates = InetAddress.getAllByName(host);
-            if (candidates.length == 0)
-                throw new UnknownHostException(host);
-            for (final InetAddress addr : candidates) {
-                if (addr instanceof Inet4Address) {
-                    resolvedHost = addr;
-                    break;
+    /**
+     * Generate an {@code InetEndpoint} instance with the same port and the host resolved using DNS
+     * to a numeric address. If the host is already numeric, the existing instance may be returned.
+     * Because this function may perform network I/O, it must not be called from the main thread.
+     *
+     * @return the resolved endpoint, or {@link Optional#empty()}
+     */
+    public Optional<InetEndpoint> getResolved() {
+        if (isResolved)
+            return Optional.of(this);
+        synchronized (lock) {
+            //TODO(zx2c4): Implement a real timeout mechanism using DNS TTL
+            if (Duration.between(lastResolution, Instant.now()).toMinutes() > 1) {
+                try {
+                    // Prefer v4 endpoints over v6 to work around DNS64 and IPv6 NAT issues.
+                    final InetAddress[] candidates = InetAddress.getAllByName(host);
+                    InetAddress address = candidates[0];
+                    for (final InetAddress candidate : candidates) {
+                        if (candidate instanceof Inet4Address) {
+                            address = candidate;
+                            break;
+                        }
+                    }
+                    resolved = new InetEndpoint(address.getHostAddress(), true, port);
+                    lastResolution = Instant.now();
+                } catch (final UnknownHostException e) {
+                    resolved = null;
                 }
             }
-            if (resolvedHost == null)
-                resolvedHost = candidates[0];
+            return Optional.ofNullable(resolved);
         }
-        return String.format(resolvedHost instanceof Inet6Address ?
-                "[%s]:%d" : "%s:%d", resolvedHost.getHostAddress(), port);
     }
 
-    @SuppressLint("DefaultLocale")
-    public String getEndpoint() {
-        return String.format(host.contains(":") && !host.contains("[") ?
-                "[%s]:%d" : "%s:%d", host, port);
+    @Override
+    public int hashCode() {
+        return host.hashCode() ^ port;
+    }
+
+    @Override
+    public String toString() {
+        final boolean isBareIpv6 = isResolved && BARE_IPV6.matcher(host).matches();
+        return (isBareIpv6 ? '[' + host + ']' : host) + ':' + port;
     }
 }
diff --git a/app/src/main/java/com/wireguard/config/InetNetwork.java b/app/src/main/java/com/wireguard/config/InetNetwork.java
index 836a1335..9e5e8c64 100644
--- a/app/src/main/java/com/wireguard/config/InetNetwork.java
+++ b/app/src/main/java/com/wireguard/config/InetNetwork.java
@@ -7,26 +7,36 @@ package com.wireguard.config;
 
 import java.net.Inet4Address;
 import java.net.InetAddress;
-import java.util.Objects;
 
-public class InetNetwork {
+/**
+ * An Internet network, denoted by its address and netmask
+ * <p>
+ * Instances of this class are immutable.
+ */
+public final class InetNetwork {
     private final InetAddress address;
     private final int mask;
 
-    public InetNetwork(final String input) {
-        final int slash = input.lastIndexOf('/');
+    private InetNetwork(final InetAddress address, final int mask) {
+        this.address = address;
+        this.mask = mask;
+    }
+
+    public static InetNetwork parse(final String network) {
+        final int slash = network.lastIndexOf('/');
         final int rawMask;
         final String rawAddress;
         if (slash >= 0) {
-            rawMask = Integer.parseInt(input.substring(slash + 1), 10);
-            rawAddress = input.substring(0, slash);
+            rawMask = Integer.parseInt(network.substring(slash + 1), 10);
+            rawAddress = network.substring(0, slash);
         } else {
             rawMask = -1;
-            rawAddress = input;
+            rawAddress = network;
         }
-        address = InetAddresses.parse(rawAddress);
+        final InetAddress address = InetAddresses.parse(rawAddress);
         final int maxMask = (address instanceof Inet4Address) ? 32 : 128;
-        mask = rawMask >= 0 && rawMask <= maxMask ? rawMask : maxMask;
+        final int mask = rawMask >= 0 && rawMask <= maxMask ? rawMask : maxMask;
+        return new InetNetwork(address, mask);
     }
 
     @Override
@@ -34,7 +44,7 @@ public class InetNetwork {
         if (!(obj instanceof InetNetwork))
             return false;
         final InetNetwork other = (InetNetwork) obj;
-        return Objects.equals(address, other.address) && mask == other.mask;
+        return address.equals(other.address) && mask == other.mask;
     }
 
     public InetAddress getAddress() {
diff --git a/app/src/main/java/com/wireguard/config/Interface.java b/app/src/main/java/com/wireguard/config/Interface.java
index aa1d986b..dc1a291d 100644
--- a/app/src/main/java/com/wireguard/config/Interface.java
+++ b/app/src/main/java/com/wireguard/config/Interface.java
@@ -5,395 +5,345 @@
 
 package com.wireguard.config;
 
-import android.content.Context;
-import android.databinding.BaseObservable;
-import android.databinding.Bindable;
-import android.os.Parcel;
-import android.os.Parcelable;
 import android.support.annotation.Nullable;
 
-import com.wireguard.android.Application;
-import com.wireguard.android.BR;
-import com.wireguard.android.R;
-import com.wireguard.crypto.Keypair;
+import com.wireguard.crypto.Key;
+import com.wireguard.crypto.KeyPair;
 
 import java.net.InetAddress;
-import java.util.ArrayList;
-import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Objects;
+import java.util.Set;
+
+import java9.util.Lists;
+import java9.util.Optional;
+import java9.util.stream.Collectors;
+import java9.util.stream.Stream;
+import java9.util.stream.StreamSupport;
 
 /**
- * Represents the configuration for a WireGuard interface (an [Interface] block).
+ * Represents the configuration for a WireGuard interface (an [Interface] block). Interfaces must
+ * have a private key (used to initialize a {@code KeyPair}), and may optionally have several other
+ * attributes.
+ * <p>
+ * Instances of this class are immutable.
  */
-
-public class Interface {
-    private final List<InetNetwork> addressList;
-    private final Context context = Application.get();
-    private final List<InetAddress> dnsList;
-    private final List<String> excludedApplications;
-    @Nullable private Keypair keypair;
-    private int listenPort;
-    private int mtu;
-
-    public Interface() {
-        addressList = new ArrayList<>();
-        dnsList = new ArrayList<>();
-        excludedApplications = new ArrayList<>();
+public final class Interface {
+    private static final int MAX_UDP_PORT = 65535;
+    private static final int MIN_UDP_PORT = 0;
+
+    private final Set<InetNetwork> addresses;
+    private final Set<InetAddress> dnsServers;
+    private final Set<String> excludedApplications;
+    private final KeyPair keyPair;
+    private final Optional<Integer> listenPort;
+    private final Optional<Integer> mtu;
+
+    private Interface(final Builder builder) {
+        // Defensively copy to ensure immutability even if the Builder is reused.
+        addresses = Collections.unmodifiableSet(new LinkedHashSet<>(builder.addresses));
+        dnsServers = Collections.unmodifiableSet(new LinkedHashSet<>(builder.dnsServers));
+        excludedApplications = Collections.unmodifiableSet(new LinkedHashSet<>(builder.excludedApplications));
+        keyPair = Objects.requireNonNull(builder.keyPair, "Interfaces must have a private key");
+        listenPort = builder.listenPort;
+        mtu = builder.mtu;
     }
 
-    private void addAddresses(@Nullable final String[] addresses) {
-        if (addresses != null && addresses.length > 0) {
-            for (final String addr : addresses) {
-                if (addr.isEmpty())
-                    throw new IllegalArgumentException(context.getString(R.string.tunnel_error_empty_interface_address));
-                addressList.add(new InetNetwork(addr));
+    /**
+     * Parses an series of "KEY = VALUE" lines into an {@code Interface}. Throws
+     * {@link ParseException} if the input is not well-formed or contains unknown attributes.
+     *
+     * @param lines An iterable sequence of lines, containing at least a private key attribute
+     * @return An {@code Interface} with all of the attributes from {@code lines} set
+     */
+    public static Interface parse(final Iterable<? extends CharSequence> lines) throws ParseException {
+        final Builder builder = new Builder();
+        for (final CharSequence line : lines) {
+            final Attribute attribute = Attribute.parse(line)
+                    .orElseThrow(() -> new ParseException("[Interface]", line, "Syntax error"));
+            switch (attribute.getKey().toLowerCase()) {
+                case "address":
+                    builder.parseAddresses(attribute.getValue());
+                    break;
+                case "dns":
+                    builder.parseDnsServers(attribute.getValue());
+                    break;
+                case "excludedapplications":
+                    builder.parseExcludedApplications(attribute.getValue());
+                    break;
+                case "listenport":
+                    builder.parseListenPort(attribute.getValue());
+                    break;
+                case "mtu":
+                    builder.parseMtu(attribute.getValue());
+                    break;
+                case "privatekey":
+                    builder.parsePrivateKey(attribute.getValue());
+                    break;
+                default:
+                    throw new ParseException("[Interface]", attribute.getKey(), "Unknown attribute");
             }
         }
+        return builder.build();
     }
 
-    private void addDnses(@Nullable final String[] dnses) {
-        if (dnses != null && dnses.length > 0) {
-            for (final String dns : dnses) {
-                dnsList.add(InetAddresses.parse(dns));
-            }
-        }
-    }
-
-    private void addExcludedApplications(@Nullable final String[] applications) {
-        if (applications != null && applications.length > 0) {
-            excludedApplications.addAll(Arrays.asList(applications));
-        }
-    }
-
-    @Nullable
-    private String getAddressString() {
-        if (addressList.isEmpty())
-            return null;
-        return Attribute.iterableToString(addressList);
-    }
-
-    public InetNetwork[] getAddresses() {
-        return addressList.toArray(new InetNetwork[addressList.size()]);
-    }
-
-    @Nullable
-    private String getDnsString() {
-        if (dnsList.isEmpty())
-            return null;
-        return Attribute.iterableToString(getDnsStrings());
+    @Override
+    public boolean equals(final Object obj) {
+        if (!(obj instanceof Interface))
+            return false;
+        final Interface other = (Interface) obj;
+        return addresses.equals(other.addresses)
+                && dnsServers.equals(other.dnsServers)
+                && excludedApplications.equals(other.excludedApplications)
+                && keyPair.equals(other.keyPair)
+                && listenPort.equals(other.listenPort)
+                && mtu.equals(other.mtu);
     }
 
-    private List<String> getDnsStrings() {
-        final List<String> strings = new ArrayList<>();
-        for (final InetAddress addr : dnsList)
-            strings.add(addr.getHostAddress());
-        return strings;
+    /**
+     * Returns the set of IP addresses assigned to the interface.
+     *
+     * @return a set of {@link InetNetwork}s
+     */
+    public Set<InetNetwork> getAddresses() {
+        // The collection is already immutable.
+        return addresses;
     }
 
-    public InetAddress[] getDnses() {
-        return dnsList.toArray(new InetAddress[dnsList.size()]);
+    /**
+     * Returns the set of DNS servers associated with the interface.
+     *
+     * @return a set of {@link InetAddress}es
+     */
+    public Set<InetAddress> getDnsServers() {
+        // The collection is already immutable.
+        return dnsServers;
     }
 
-    public String[] getExcludedApplications() {
-        return excludedApplications.toArray(new String[excludedApplications.size()]);
+    /**
+     * Returns the set of applications excluded from using the interface.
+     *
+     * @return a set of package names
+     */
+    public Set<String> getExcludedApplications() {
+        // The collection is already immutable.
+        return excludedApplications;
     }
 
-    @Nullable
-    private String getExcludedApplicationsString() {
-        if (excludedApplications.isEmpty())
-            return null;
-        return Attribute.iterableToString(excludedApplications);
+    /**
+     * Returns the public/private key pair used by the interface.
+     *
+     * @return a key pair
+     */
+    public KeyPair getKeyPair() {
+        return keyPair;
     }
 
-    public int getListenPort() {
+    /**
+     * Returns the UDP port number that the WireGuard interface will listen on.
+     *
+     * @return a UDP port number, or {@code Optional.empty()} if none is configured
+     */
+    public Optional<Integer> getListenPort() {
         return listenPort;
     }
 
-    @Nullable
-    private String getListenPortString() {
-        if (listenPort == 0)
-            return null;
-        return Integer.valueOf(listenPort).toString();
-    }
-
-    public int getMtu() {
+    /**
+     * Returns the MTU used for the WireGuard interface.
+     *
+     * @return the MTU, or {@code Optional.empty()} if none is configured
+     */
+    public Optional<Integer> getMtu() {
         return mtu;
     }
 
-    @Nullable
-    private String getMtuString() {
-        if (mtu == 0)
-            return null;
-        return Integer.toString(mtu);
-    }
-
-    @Nullable
-    public String getPrivateKey() {
-        if (keypair == null)
-            return null;
-        return keypair.getPrivateKey();
-    }
-
-    @Nullable
-    public String getPublicKey() {
-        if (keypair == null)
-            return null;
-        return keypair.getPublicKey();
-    }
-
-    public void parse(final String line) {
-        final Attribute key = Attribute.match(line);
-        if (key == null)
-            throw new IllegalArgumentException(String.format(context.getString(R.string.tunnel_error_interface_parse_failed), line));
-        switch (key) {
-            case ADDRESS:
-                addAddresses(key.parseList(line));
-                break;
-            case DNS:
-                addDnses(key.parseList(line));
-                break;
-            case EXCLUDED_APPLICATIONS:
-                addExcludedApplications(key.parseList(line));
-                break;
-            case LISTEN_PORT:
-                setListenPortString(key.parse(line));
-                break;
-            case MTU:
-                setMtuString(key.parse(line));
-                break;
-            case PRIVATE_KEY:
-                setPrivateKey(key.parse(line));
-                break;
-            default:
-                throw new IllegalArgumentException(line);
-        }
-    }
-
-    private void setAddressString(@Nullable final String addressString) {
-        addressList.clear();
-        addAddresses(Attribute.stringToList(addressString));
-    }
-
-    private void setDnsString(@Nullable final String dnsString) {
-        dnsList.clear();
-        addDnses(Attribute.stringToList(dnsString));
-    }
-
-    private void setExcludedApplicationsString(@Nullable final String applicationsString) {
-        excludedApplications.clear();
-        addExcludedApplications(Attribute.stringToList(applicationsString));
-    }
-
-    private void setListenPort(final int listenPort) {
-        this.listenPort = listenPort;
-    }
-
-    private void setListenPortString(@Nullable final String port) {
-        if (port != null && !port.isEmpty())
-            setListenPort(Integer.parseInt(port, 10));
-        else
-            setListenPort(0);
-    }
-
-    private void setMtu(final int mtu) {
-        this.mtu = mtu;
-    }
-
-    private void setMtuString(@Nullable final String mtu) {
-        if (mtu != null && !mtu.isEmpty())
-            setMtu(Integer.parseInt(mtu, 10));
-        else
-            setMtu(0);
-    }
-
-    private void setPrivateKey(@Nullable String privateKey) {
-        if (privateKey != null && privateKey.isEmpty())
-            privateKey = null;
-        keypair = privateKey == null ? null : new Keypair(privateKey);
+    @Override
+    public int hashCode() {
+        int hash = 1;
+        hash = 31 * hash + addresses.hashCode();
+        hash = 31 * hash + dnsServers.hashCode();
+        hash = 31 * hash + excludedApplications.hashCode();
+        hash = 31 * hash + keyPair.hashCode();
+        hash = 31 * hash + listenPort.hashCode();
+        hash = 31 * hash + mtu.hashCode();
+        return hash;
     }
 
+    /**
+     * Converts the {@code Interface} into a string suitable for debugging purposes. The {@code
+     * Interface} is identified by its public key and (if set) the port used for its UDP socket.
+     *
+     * @return A concise single-line identifier for the {@code Interface}
+     */
     @Override
     public String toString() {
-        final StringBuilder sb = new StringBuilder().append("[Interface]\n");
-        if (!addressList.isEmpty())
-            sb.append(Attribute.ADDRESS.composeWith(addressList));
-        if (!dnsList.isEmpty())
-            sb.append(Attribute.DNS.composeWith(getDnsStrings()));
-        if (!excludedApplications.isEmpty())
-            sb.append(Attribute.EXCLUDED_APPLICATIONS.composeWith(excludedApplications));
-        if (listenPort != 0)
-            sb.append(Attribute.LISTEN_PORT.composeWith(listenPort));
-        if (mtu != 0)
-            sb.append(Attribute.MTU.composeWith(mtu));
-        if (keypair != null)
-            sb.append(Attribute.PRIVATE_KEY.composeWith(keypair.getPrivateKey()));
+        final StringBuilder sb = new StringBuilder("(Interface ");
+        sb.append(keyPair.getPublicKey().toBase64());
+        listenPort.ifPresent(lp -> sb.append(" @").append(lp));
+        sb.append(')');
         return sb.toString();
     }
 
-    public static class Observable extends BaseObservable implements Parcelable {
-        public static final Creator<Observable> CREATOR = new Creator<Observable>() {
-            @Override
-            public Observable createFromParcel(final Parcel in) {
-                return new Observable(in);
-            }
-
-            @Override
-            public Observable[] newArray(final int size) {
-                return new Observable[size];
-            }
-        };
-        @Nullable private String addresses;
-        @Nullable private String dnses;
-        @Nullable private String excludedApplications;
-        @Nullable private String listenPort;
-        @Nullable private String mtu;
-        @Nullable private String privateKey;
-        @Nullable private String publicKey;
-
-        public Observable(@Nullable final Interface parent) {
-            if (parent != null)
-                loadData(parent);
-        }
-
-        private Observable(final Parcel in) {
-            addresses = in.readString();
-            dnses = in.readString();
-            publicKey = in.readString();
-            privateKey = in.readString();
-            listenPort = in.readString();
-            mtu = in.readString();
-            excludedApplications = in.readString();
-        }
-
-        public void commitData(final Interface parent) {
-            parent.setAddressString(addresses);
-            parent.setDnsString(dnses);
-            parent.setExcludedApplicationsString(excludedApplications);
-            parent.setPrivateKey(privateKey);
-            parent.setListenPortString(listenPort);
-            parent.setMtuString(mtu);
-            loadData(parent);
-            notifyChange();
-        }
-
-        @Override
-        public int describeContents() {
-            return 0;
+    /**
+     * Converts the {@code Interface} into a string suitable for inclusion in a {@code wg-quick}
+     * configuration file.
+     *
+     * @return The {@code Interface} represented as a series of "Key = Value" lines
+     */
+    public String toWgQuickString() {
+        final StringBuilder sb = new StringBuilder();
+        if (!addresses.isEmpty())
+            sb.append("Address = ").append(Attribute.join(addresses)).append('\n');
+        if (!dnsServers.isEmpty()) {
+            final List<String> dnsServerStrings = StreamSupport.stream(dnsServers)
+                    .map(InetAddress::getHostAddress)
+                    .collect(Collectors.toUnmodifiableList());
+            sb.append("DNS = ").append(Attribute.join(dnsServerStrings)).append('\n');
         }
+        if (!excludedApplications.isEmpty())
+            sb.append("ExcludedApplications = ").append(Attribute.join(excludedApplications)).append('\n');
+        listenPort.ifPresent(lp -> sb.append("ListenPort = ").append(lp).append('\n'));
+        mtu.ifPresent(m -> sb.append("MTU = ").append(m).append('\n'));
+        sb.append("PrivateKey = ").append(keyPair.getPrivateKey().toBase64()).append('\n');
+        return sb.toString();
+    }
 
-        public void generateKeypair() {
-            final Keypair keypair = new Keypair();
-            privateKey = keypair.getPrivateKey();
-            publicKey = keypair.getPublicKey();
-            notifyPropertyChanged(BR.privateKey);
-            notifyPropertyChanged(BR.publicKey);
-        }
+    /**
+     * Serializes the {@code Interface} for use with the WireGuard cross-platform userspace API.
+     * Note that not all attributes are included in this representation.
+     *
+     * @return the {@code Interface} represented as a series of "KEY=VALUE" lines
+     */
+    public String toWgUserspaceString() {
+        final StringBuilder sb = new StringBuilder();
+        sb.append("private_key=").append(keyPair.getPrivateKey().toHex()).append('\n');
+        listenPort.ifPresent(lp -> sb.append("listen_port=").append(lp).append('\n'));
+        return sb.toString();
+    }
 
-        @Nullable
-        @Bindable
-        public String getAddresses() {
-            return addresses;
+    @SuppressWarnings("UnusedReturnValue")
+    public static final class Builder {
+        // Defaults to an empty set.
+        private final Set<InetNetwork> addresses = new LinkedHashSet<>();
+        // Defaults to an empty set.
+        private final Set<InetAddress> dnsServers = new LinkedHashSet<>();
+        // Defaults to an empty set.
+        private final Set<String> excludedApplications = new LinkedHashSet<>();
+        // No default; must be provided before building.
+        @Nullable private KeyPair keyPair;
+        // Defaults to not present.
+        private Optional<Integer> listenPort = Optional.empty();
+        // Defaults to not present.
+        private Optional<Integer> mtu = Optional.empty();
+
+        public Builder addAddress(final InetNetwork address) {
+            addresses.add(address);
+            return this;
         }
 
-        @Nullable
-        @Bindable
-        public String getDnses() {
-            return dnses;
+        public Builder addAddresses(final Collection<InetNetwork> addresses) {
+            this.addresses.addAll(addresses);
+            return this;
         }
 
-        @Nullable
-        @Bindable
-        public String getExcludedApplications() {
-            return excludedApplications;
+        public Builder addDnsServer(final InetAddress dnsServer) {
+            dnsServers.add(dnsServer);
+            return this;
         }
 
-        @Bindable
-        public int getExcludedApplicationsCount() {
-            return Attribute.stringToList(excludedApplications).length;
+        public Builder addDnsServers(final Collection<? extends InetAddress> dnsServers) {
+            this.dnsServers.addAll(dnsServers);
+            return this;
         }
 
-        @Nullable
-        @Bindable
-        public String getListenPort() {
-            return listenPort;
+        public Interface build() {
+            return new Interface(this);
         }
 
-        @Nullable
-        @Bindable
-        public String getMtu() {
-            return mtu;
+        public Builder excludeApplication(final String application) {
+            excludedApplications.add(application);
+            return this;
         }
 
-        @Nullable
-        @Bindable
-        public String getPrivateKey() {
-            return privateKey;
+        public Builder excludeApplications(final Collection<String> applications) {
+            excludedApplications.addAll(applications);
+            return this;
         }
 
-        @Nullable
-        @Bindable
-        public String getPublicKey() {
-            return publicKey;
+        public Builder parseAddresses(final CharSequence addresses) throws ParseException {
+            try {
+                final List<InetNetwork> parsed = Stream.of(Attribute.split(addresses))
+                        .map(InetNetwork::parse)
+                        .collect(Collectors.toUnmodifiableList());
+                return addAddresses(parsed);
+            } catch (final IllegalArgumentException e) {
+                throw new ParseException("Address", addresses, e);
+            }
         }
 
-        private void loadData(final Interface parent) {
-            addresses = parent.getAddressString();
-            dnses = parent.getDnsString();
-            excludedApplications = parent.getExcludedApplicationsString();
-            publicKey = parent.getPublicKey();
-            privateKey = parent.getPrivateKey();
-            listenPort = parent.getListenPortString();
-            mtu = parent.getMtuString();
+        public Builder parseDnsServers(final CharSequence dnsServers) throws ParseException {
+            try {
+                final List<InetAddress> parsed = Stream.of(Attribute.split(dnsServers))
+                        .map(InetAddresses::parse)
+                        .collect(Collectors.toUnmodifiableList());
+                return addDnsServers(parsed);
+            } catch (final IllegalArgumentException e) {
+                throw new ParseException("DNS", dnsServers, e);
+            }
         }
 
-        public void setAddresses(final String addresses) {
-            this.addresses = addresses;
-            notifyPropertyChanged(BR.addresses);
+        public Builder parseExcludedApplications(final CharSequence apps) throws ParseException {
+            try {
+                return excludeApplications(Lists.of(Attribute.split(apps)));
+            } catch (final IllegalArgumentException e) {
+                throw new ParseException("ExcludedApplications", apps, e);
+            }
         }
 
-        public void setDnses(final String dnses) {
-            this.dnses = dnses;
-            notifyPropertyChanged(BR.dnses);
+        public Builder parseListenPort(final String listenPort) throws ParseException {
+            try {
+                return setListenPort(Integer.parseInt(listenPort));
+            } catch (final IllegalArgumentException e) {
+                throw new ParseException("ListenPort", listenPort, e);
+            }
         }
 
-        public void setExcludedApplications(final String excludedApplications) {
-            this.excludedApplications = excludedApplications;
-            notifyPropertyChanged(BR.excludedApplications);
-            notifyPropertyChanged(BR.excludedApplicationsCount);
+        public Builder parseMtu(final String mtu) throws ParseException {
+            try {
+                return setMtu(Integer.parseInt(mtu));
+            } catch (final IllegalArgumentException e) {
+                throw new ParseException("MTU", mtu, e);
+            }
         }
 
-        public void setListenPort(final String listenPort) {
-            this.listenPort = listenPort;
-            notifyPropertyChanged(BR.listenPort);
+        public Builder parsePrivateKey(final String privateKey) throws ParseException {
+            try {
+                return setKeyPair(new KeyPair(Key.fromBase64(privateKey)));
+            } catch (final Key.KeyFormatException e) {
+                throw new ParseException("PrivateKey", "(omitted)", e);
+            }
         }
 
-        public void setMtu(final String mtu) {
-            this.mtu = mtu;
-            notifyPropertyChanged(BR.mtu);
+        public Builder setKeyPair(final KeyPair keyPair) {
+            this.keyPair = keyPair;
+            return this;
         }
 
-        public void setPrivateKey(final String privateKey) {
-            this.privateKey = privateKey;
-
-            try {
-                publicKey = new Keypair(privateKey).getPublicKey();
-            } catch (final IllegalArgumentException ignored) {
-                publicKey = "";
-            }
-
-            notifyPropertyChanged(BR.privateKey);
-            notifyPropertyChanged(BR.publicKey);
+        public Builder setListenPort(final int listenPort) {
+            if (listenPort < MIN_UDP_PORT || listenPort > MAX_UDP_PORT)
+                throw new IllegalArgumentException("ListenPort must be a valid UDP port number");
+            this.listenPort = listenPort == 0 ? Optional.empty() : Optional.of(listenPort);
+            return this;
         }
 
-        @Override
-        public void writeToParcel(final Parcel dest, final int flags) {
-            dest.writeString(addresses);
-            dest.writeString(dnses);
-            dest.writeString(publicKey);
-            dest.writeString(privateKey);
-            dest.writeString(listenPort);
-            dest.writeString(mtu);
-            dest.writeString(excludedApplications);
+        public Builder setMtu(final int mtu) {
+            if (mtu < 0)
+                throw new IllegalArgumentException("MTU must not be negative");
+            this.mtu = mtu == 0 ? Optional.empty() : Optional.of(mtu);
+            return this;
         }
     }
 }
diff --git a/app/src/main/java/com/wireguard/config/ParseException.java b/app/src/main/java/com/wireguard/config/ParseException.java
new file mode 100644
index 00000000..1fccb534
--- /dev/null
+++ b/app/src/main/java/com/wireguard/config/ParseException.java
@@ -0,0 +1,41 @@
+/*
+ * Copyright © 2018 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.config;
+
+/**
+ * An exception representing a failure to parse an element of a WireGuard configuration. The context
+ * for this failure can be retrieved with {@link #getContext}, and the text that failed to parse can
+ * be retrieved with {@link #getText}.
+ */
+public class ParseException extends Exception {
+    private final String context;
+    private final CharSequence text;
+
+    public ParseException(final String context, final CharSequence text, final String message) {
+        super(message);
+        this.context = context;
+        this.text = text;
+    }
+
+    public ParseException(final String context, final CharSequence text, final Throwable cause) {
+        super(cause.getMessage(), cause);
+        this.context = context;
+        this.text = text;
+    }
+
+    public ParseException(final String context, final CharSequence text) {
+        this.context = context;
+        this.text = text;
+    }
+
+    public String getContext() {
+        return context;
+    }
+
+    public CharSequence getText() {
+        return text;
+    }
+}
diff --git a/app/src/main/java/com/wireguard/config/Peer.java b/app/src/main/java/com/wireguard/config/Peer.java
index 5cf0283c..50135fb0 100644
--- a/app/src/main/java/com/wireguard/config/Peer.java
+++ b/app/src/main/java/com/wireguard/config/Peer.java
@@ -5,363 +5,291 @@
 
 package com.wireguard.config;
 
-import android.annotation.SuppressLint;
-import android.content.Context;
-import android.databinding.BaseObservable;
-import android.databinding.Bindable;
-import android.os.Parcel;
-import android.os.Parcelable;
 import android.support.annotation.Nullable;
 
-import com.android.databinding.library.baseAdapters.BR;
-import com.wireguard.android.Application;
-import com.wireguard.android.R;
-import com.wireguard.crypto.KeyEncoding;
-
-import java.net.Inet6Address;
-import java.net.InetSocketAddress;
-import java.net.URI;
-import java.net.URISyntaxException;
-import java.net.UnknownHostException;
-import java.util.ArrayList;
-import java.util.Arrays;
+import com.wireguard.crypto.Key;
+
 import java.util.Collection;
-import java.util.HashSet;
+import java.util.Collections;
+import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Objects;
+import java.util.Set;
 
-import java9.lang.Iterables;
+import java9.util.Optional;
+import java9.util.stream.Collectors;
+import java9.util.stream.Stream;
 
 /**
- * Represents the configuration for a WireGuard peer (a [Peer] block).
+ * Represents the configuration for a WireGuard peer (a [Peer] block). Peers must have a public key,
+ * and may optionally have several other attributes.
+ * <p>
+ * Instances of this class are immutable.
  */
-
-public class Peer {
-    private final List<InetNetwork> allowedIPsList;
-    private final Context context = Application.get();
-    @Nullable private InetEndpoint endpoint;
-    private int persistentKeepalive;
-    @Nullable private String preSharedKey;
-    @Nullable private String publicKey;
-
-    public Peer() {
-        allowedIPsList = new ArrayList<>();
+public final class Peer {
+    private final Set<InetNetwork> allowedIps;
+    private final Optional<InetEndpoint> endpoint;
+    private final Optional<Integer> persistentKeepalive;
+    private final Optional<Key> preSharedKey;
+    private final Key publicKey;
+
+    private Peer(final Builder builder) {
+        // Defensively copy to ensure immutability even if the Builder is reused.
+        allowedIps = Collections.unmodifiableSet(new LinkedHashSet<>(builder.allowedIps));
+        endpoint = builder.endpoint;
+        persistentKeepalive = builder.persistentKeepalive;
+        preSharedKey = builder.preSharedKey;
+        publicKey = Objects.requireNonNull(builder.publicKey, "Peers must have a public key");
     }
 
-    private void addAllowedIPs(@Nullable final String[] allowedIPs) {
-        if (allowedIPs != null && allowedIPs.length > 0) {
-            for (final String allowedIP : allowedIPs) {
-                allowedIPsList.add(new InetNetwork(allowedIP));
+    /**
+     * Parses an series of "KEY = VALUE" lines into a {@code Peer}. Throws {@link ParseException} if
+     * the input is not well-formed or contains unknown attributes.
+     *
+     * @param lines an iterable sequence of lines, containing at least a public key attribute
+     * @return a {@code Peer} with all of its attributes set from {@code lines}
+     */
+    public static Peer parse(final Iterable<? extends CharSequence> lines) throws ParseException {
+        final Builder builder = new Builder();
+        for (final CharSequence line : lines) {
+            final Attribute attribute = Attribute.parse(line)
+                    .orElseThrow(() -> new ParseException("[Peer]", line, "Syntax error"));
+            switch (attribute.getKey().toLowerCase()) {
+                case "allowedips":
+                    builder.parseAllowedIPs(attribute.getValue());
+                    break;
+                case "endpoint":
+                    builder.parseEndpoint(attribute.getValue());
+                    break;
+                case "persistentkeepalive":
+                    builder.parsePersistentKeepalive(attribute.getValue());
+                    break;
+                case "presharedkey":
+                    builder.parsePreSharedKey(attribute.getValue());
+                    break;
+                case "publickey":
+                    builder.parsePublicKey(attribute.getValue());
+                    break;
+                default:
+                    throw new ParseException("[Peer]", line, "Unknown attribute");
             }
         }
+        return builder.build();
     }
 
-    public InetNetwork[] getAllowedIPs() {
-        return allowedIPsList.toArray(new InetNetwork[allowedIPsList.size()]);
+    @Override
+    public boolean equals(final Object obj) {
+        if (!(obj instanceof Peer))
+            return false;
+        final Peer other = (Peer) obj;
+        return allowedIps.equals(other.allowedIps)
+                && endpoint.equals(other.endpoint)
+                && persistentKeepalive.equals(other.persistentKeepalive)
+                && preSharedKey.equals(other.preSharedKey)
+                && publicKey.equals(other.publicKey);
     }
 
-    @Nullable
-    private String getAllowedIPsString() {
-        if (allowedIPsList.isEmpty())
-            return null;
-        return Attribute.iterableToString(allowedIPsList);
+    /**
+     * Returns the peer's set of allowed IPs.
+     *
+     * @return the set of allowed IPs
+     */
+    public Set<InetNetwork> getAllowedIps() {
+        // The collection is already immutable.
+        return allowedIps;
     }
 
-    @Nullable
-    public InetEndpoint getEndpoint() {
+    /**
+     * Returns the peer's endpoint.
+     *
+     * @return the endpoint, or {@code Optional.empty()} if none is configured
+     */
+    public Optional<InetEndpoint> getEndpoint() {
         return endpoint;
     }
 
-    @Nullable
-    private String getEndpointString() {
-        if (endpoint == null)
-            return null;
-        return endpoint.getEndpoint();
-    }
-
-    public int getPersistentKeepalive() {
+    /**
+     * Returns the peer's persistent keepalive.
+     *
+     * @return the persistent keepalive, or {@code Optional.empty()} if none is configured
+     */
+    public Optional<Integer> getPersistentKeepalive() {
         return persistentKeepalive;
     }
 
-    @Nullable
-    private String getPersistentKeepaliveString() {
-        if (persistentKeepalive == 0)
-            return null;
-        return Integer.valueOf(persistentKeepalive).toString();
-    }
-
-    @Nullable
-    public String getPreSharedKey() {
+    /**
+     * Returns the peer's pre-shared key.
+     *
+     * @return the pre-shared key, or {@code Optional.empty()} if none is configured
+     */
+    public Optional<Key> getPreSharedKey() {
         return preSharedKey;
     }
 
-    @Nullable
-    public String getPublicKey() {
+    /**
+     * Returns the peer's public key.
+     *
+     * @return the public key
+     */
+    public Key getPublicKey() {
         return publicKey;
     }
 
-    public String getResolvedEndpointString() throws UnknownHostException {
-        if (endpoint == null)
-            throw new UnknownHostException("{empty}");
-        return endpoint.getResolvedEndpoint();
-    }
-
-    public void parse(final String line) {
-        final Attribute key = Attribute.match(line);
-        if (key == null)
-            throw new IllegalArgumentException(context.getString(R.string.tunnel_error_interface_parse_failed, line));
-        switch (key) {
-            case ALLOWED_IPS:
-                addAllowedIPs(key.parseList(line));
-                break;
-            case ENDPOINT:
-                setEndpointString(key.parse(line));
-                break;
-            case PERSISTENT_KEEPALIVE:
-                setPersistentKeepaliveString(key.parse(line));
-                break;
-            case PRESHARED_KEY:
-                setPreSharedKey(key.parse(line));
-                break;
-            case PUBLIC_KEY:
-                setPublicKey(key.parse(line));
-                break;
-            default:
-                throw new IllegalArgumentException(line);
-        }
-    }
-
-    private void setAllowedIPsString(@Nullable final String allowedIPsString) {
-        allowedIPsList.clear();
-        addAllowedIPs(Attribute.stringToList(allowedIPsString));
-    }
-
-    private void setEndpoint(@Nullable final InetEndpoint endpoint) {
-        this.endpoint = endpoint;
-    }
-
-    private void setEndpointString(@Nullable final String endpoint) {
-        if (endpoint != null && !endpoint.isEmpty())
-            setEndpoint(new InetEndpoint(endpoint));
-        else
-            setEndpoint(null);
-    }
-
-    private void setPersistentKeepalive(final int persistentKeepalive) {
-        this.persistentKeepalive = persistentKeepalive;
-    }
-
-    private void setPersistentKeepaliveString(@Nullable final String persistentKeepalive) {
-        if (persistentKeepalive != null && !persistentKeepalive.isEmpty())
-            setPersistentKeepalive(Integer.parseInt(persistentKeepalive, 10));
-        else
-            setPersistentKeepalive(0);
-    }
-
-    private void setPreSharedKey(@Nullable String preSharedKey) {
-        if (preSharedKey != null && preSharedKey.isEmpty())
-            preSharedKey = null;
-        if (preSharedKey != null)
-            KeyEncoding.keyFromBase64(preSharedKey);
-        this.preSharedKey = preSharedKey;
-    }
-
-    private void setPublicKey(@Nullable String publicKey) {
-        if (publicKey != null && publicKey.isEmpty())
-            publicKey = null;
-        if (publicKey != null)
-            KeyEncoding.keyFromBase64(publicKey);
-        this.publicKey = publicKey;
+    @Override
+    public int hashCode() {
+        int hash = 1;
+        hash = 31 * hash + allowedIps.hashCode();
+        hash = 31 * hash + endpoint.hashCode();
+        hash = 31 * hash + persistentKeepalive.hashCode();
+        hash = 31 * hash + preSharedKey.hashCode();
+        hash = 31 * hash + publicKey.hashCode();
+        return hash;
     }
 
+    /**
+     * Converts the {@code Peer} into a string suitable for debugging purposes. The {@code Peer} is
+     * identified by its public key and (if known) its endpoint.
+     *
+     * @return a concise single-line identifier for the {@code Peer}
+     */
     @Override
     public String toString() {
-        final StringBuilder sb = new StringBuilder().append("[Peer]\n");
-        if (!allowedIPsList.isEmpty())
-            sb.append(Attribute.ALLOWED_IPS.composeWith(allowedIPsList));
-        if (endpoint != null)
-            sb.append(Attribute.ENDPOINT.composeWith(getEndpointString()));
-        if (persistentKeepalive != 0)
-            sb.append(Attribute.PERSISTENT_KEEPALIVE.composeWith(persistentKeepalive));
-        if (preSharedKey != null)
-            sb.append(Attribute.PRESHARED_KEY.composeWith(preSharedKey));
-        if (publicKey != null)
-            sb.append(Attribute.PUBLIC_KEY.composeWith(publicKey));
+        final StringBuilder sb = new StringBuilder("(Peer ");
+        sb.append(publicKey.toBase64());
+        endpoint.ifPresent(ep -> sb.append(" @").append(ep));
+        sb.append(')');
         return sb.toString();
     }
 
-    public static class Observable extends BaseObservable implements Parcelable {
-        public static final Creator<Observable> CREATOR = new Creator<Observable>() {
-            @Override
-            public Observable createFromParcel(final Parcel in) {
-                return new Observable(in);
-            }
-
-            @Override
-            public Observable[] newArray(final int size) {
-                return new Observable[size];
-            }
-        };
-        private static final List<String> DEFAULT_ROUTE_MOD_RFC1918_V4 = Arrays.asList("0.0.0.0/5", "8.0.0.0/7", "11.0.0.0/8", "12.0.0.0/6", "16.0.0.0/4", "32.0.0.0/3", "64.0.0.0/2", "128.0.0.0/3", "160.0.0.0/5", "168.0.0.0/6", "172.0.0.0/12", "172.32.0.0/11", "172.64.0.0/10", "172.128.0.0/9", "173.0.0.0/8", "174.0.0.0/7", "176.0.0.0/4", "192.0.0.0/9", "192.128.0.0/11", "192.160.0.0/13", "192.169.0.0/16", "192.170.0.0/15", "192.172.0.0/14", "192.176.0.0/12", "192.192.0.0/10", "193.0.0.0/8", "194.0.0.0/7", "196.0.0.0/6", "200.0.0.0/5", "208.0.0.0/4");
-        private static final String DEFAULT_ROUTE_V4 = "0.0.0.0/0";
-        private final List<String> interfaceDNSRoutes = new ArrayList<>();
-        @Nullable private String allowedIPs;
-        @Nullable private String endpoint;
-        private int numSiblings;
-        @Nullable private String persistentKeepalive;
-        @Nullable private String preSharedKey;
-        @Nullable private String publicKey;
-
-        public Observable(final Peer parent) {
-            loadData(parent);
-        }
-
-        private Observable(final Parcel in) {
-            allowedIPs = in.readString();
-            endpoint = in.readString();
-            persistentKeepalive = in.readString();
-            preSharedKey = in.readString();
-            publicKey = in.readString();
-            numSiblings = in.readInt();
-            in.readStringList(interfaceDNSRoutes);
-        }
-
-        public static Observable newInstance() {
-            return new Observable(new Peer());
-        }
-
-        public void commitData(final Peer parent) {
-            parent.setAllowedIPsString(allowedIPs);
-            parent.setEndpointString(endpoint);
-            parent.setPersistentKeepaliveString(persistentKeepalive);
-            parent.setPreSharedKey(preSharedKey);
-            parent.setPublicKey(publicKey);
-            if (parent.getPublicKey() == null)
-                throw new IllegalArgumentException(Application.get().getString(R.string.tunnel_error_empty_peer_public_key));
-            loadData(parent);
-            notifyChange();
-        }
-
-        @Override
-        public int describeContents() {
-            return 0;
-        }
-
-        @Bindable @Nullable
-        public String getAllowedIPs() {
-            return allowedIPs;
-        }
-
-        @Bindable
-        public boolean getCanToggleExcludePrivateIPs() {
-            final Collection<String> ips = Arrays.asList(Attribute.stringToList(allowedIPs));
-            return numSiblings == 0 && (ips.contains(DEFAULT_ROUTE_V4) || ips.containsAll(DEFAULT_ROUTE_MOD_RFC1918_V4));
-        }
+    /**
+     * Converts the {@code Peer} into a string suitable for inclusion in a {@code wg-quick}
+     * configuration file.
+     *
+     * @return the {@code Peer} represented as a series of "Key = Value" lines
+     */
+    public String toWgQuickString() {
+        final StringBuilder sb = new StringBuilder();
+        if (!allowedIps.isEmpty())
+            sb.append("AllowedIPs = ").append(Attribute.join(allowedIps)).append('\n');
+        endpoint.ifPresent(ep -> sb.append("Endpoint = ").append(ep).append('\n'));
+        persistentKeepalive.ifPresent(pk -> sb.append("PersistentKeepalive = ").append(pk).append('\n'));
+        preSharedKey.ifPresent(psk -> sb.append("PreSharedKey = ").append(psk.toBase64()).append('\n'));
+        sb.append("PublicKey = ").append(publicKey.toBase64()).append('\n');
+        return sb.toString();
+    }
 
-        @Bindable @Nullable
-        public String getEndpoint() {
-            return endpoint;
-        }
+    /**
+     * Serializes the {@code Peer} for use with the WireGuard cross-platform userspace API. Note
+     * that not all attributes are included in this representation.
+     *
+     * @return the {@code Peer} represented as a series of "key=value" lines
+     */
+    public String toWgUserspaceString() {
+        final StringBuilder sb = new StringBuilder();
+        // The order here is important: public_key signifies the beginning of a new peer.
+        sb.append("public_key=").append(publicKey.toHex()).append('\n');
+        for (final InetNetwork allowedIp : allowedIps)
+            sb.append("allowed_ip=").append(allowedIp).append('\n');
+        endpoint.flatMap(InetEndpoint::getResolved).ifPresent(ep -> sb.append("endpoint=").append(ep).append('\n'));
+        persistentKeepalive.ifPresent(pk -> sb.append("persistent_keepalive_interval=").append(pk).append('\n'));
+        preSharedKey.ifPresent(psk -> sb.append("preshared_key=").append(psk.toHex()).append('\n'));
+        return sb.toString();
+    }
 
-        @Bindable
-        public boolean getIsExcludePrivateIPsOn() {
-            return numSiblings == 0 && Arrays.asList(Attribute.stringToList(allowedIPs)).containsAll(DEFAULT_ROUTE_MOD_RFC1918_V4);
+    @SuppressWarnings("UnusedReturnValue")
+    public static final class Builder {
+        // See wg(8)
+        private static final int MAX_PERSISTENT_KEEPALIVE = 65535;
+
+        // Defaults to an empty set.
+        private final Set<InetNetwork> allowedIps = new LinkedHashSet<>();
+        // Defaults to not present.
+        private Optional<InetEndpoint> endpoint = Optional.empty();
+        // Defaults to not present.
+        private Optional<Integer> persistentKeepalive = Optional.empty();
+        // Defaults to not present.
+        private Optional<Key> preSharedKey = Optional.empty();
+        // No default; must be provided before building.
+        @Nullable private Key publicKey;
+
+        public Builder addAllowedIp(final InetNetwork allowedIp) {
+            allowedIps.add(allowedIp);
+            return this;
         }
 
-        @Bindable @Nullable
-        public String getPersistentKeepalive() {
-            return persistentKeepalive;
+        public Builder addAllowedIps(final Collection<InetNetwork> allowedIps) {
+            this.allowedIps.addAll(allowedIps);
+            return this;
         }
 
-        @Bindable @Nullable
-        public String getPreSharedKey() {
-            return preSharedKey;
+        public Peer build() {
+            return new Peer(this);
         }
 
-        @Bindable @Nullable
-        public String getPublicKey() {
-            return publicKey;
+        public Builder parseAllowedIPs(final CharSequence allowedIps) throws ParseException {
+            try {
+                final List<InetNetwork> parsed = Stream.of(Attribute.split(allowedIps))
+                        .map(InetNetwork::parse)
+                        .collect(Collectors.toUnmodifiableList());
+                return addAllowedIps(parsed);
+            } catch (final IllegalArgumentException e) {
+                throw new ParseException("AllowedIPs", allowedIps, e);
+            }
         }
 
-        private void loadData(final Peer parent) {
-            allowedIPs = parent.getAllowedIPsString();
-            endpoint = parent.getEndpointString();
-            persistentKeepalive = parent.getPersistentKeepaliveString();
-            preSharedKey = parent.getPreSharedKey();
-            publicKey = parent.getPublicKey();
+        public Builder parseEndpoint(final String endpoint) throws ParseException {
+            try {
+                return setEndpoint(InetEndpoint.parse(endpoint));
+            } catch (final IllegalArgumentException e) {
+                throw new ParseException("Endpoint", endpoint, e);
+            }
         }
 
-        public void setAllowedIPs(final String allowedIPs) {
-            this.allowedIPs = allowedIPs;
-            notifyPropertyChanged(BR.allowedIPs);
-            notifyPropertyChanged(BR.canToggleExcludePrivateIPs);
-            notifyPropertyChanged(BR.isExcludePrivateIPsOn);
+        public Builder parsePersistentKeepalive(final String persistentKeepalive) throws ParseException {
+            try {
+                return setPersistentKeepalive(Integer.parseInt(persistentKeepalive));
+            } catch (final IllegalArgumentException e) {
+                throw new ParseException("PersistentKeepalive", persistentKeepalive, e);
+            }
         }
 
-        public void setEndpoint(final String endpoint) {
-            this.endpoint = endpoint;
-            notifyPropertyChanged(BR.endpoint);
+        public Builder parsePreSharedKey(final String preSharedKey) throws ParseException {
+            try {
+                return setPreSharedKey(Key.fromBase64(preSharedKey));
+            } catch (final Key.KeyFormatException e) {
+                throw new ParseException("PresharedKey", preSharedKey, e);
+            }
         }
 
-        public void setInterfaceDNSRoutes(@Nullable final String dnsServers) {
-            final Collection<String> ips = new HashSet<>(Arrays.asList(Attribute.stringToList(allowedIPs)));
-            final boolean modifyAllowedIPs = ips.containsAll(DEFAULT_ROUTE_MOD_RFC1918_V4);
-
-            ips.removeAll(interfaceDNSRoutes);
-            interfaceDNSRoutes.clear();
-            for (final String dnsServer : Attribute.stringToList(dnsServers)) {
-                if (!dnsServer.contains(":"))
-                    interfaceDNSRoutes.add(dnsServer + "/32");
+        public Builder parsePublicKey(final String publicKey) throws ParseException {
+            try {
+                return setPublicKey(Key.fromBase64(publicKey));
+            } catch (final Key.KeyFormatException e) {
+                throw new ParseException("PublicKey", publicKey, e);
             }
-            ips.addAll(interfaceDNSRoutes);
-            if (modifyAllowedIPs)
-                setAllowedIPs(Attribute.iterableToString(ips));
         }
 
-        public void setNumSiblings(final int num) {
-            numSiblings = num;
-            notifyPropertyChanged(BR.canToggleExcludePrivateIPs);
-            notifyPropertyChanged(BR.isExcludePrivateIPsOn);
+        public Builder setEndpoint(final InetEndpoint endpoint) {
+            this.endpoint = Optional.of(endpoint);
+            return this;
         }
 
-        public void setPersistentKeepalive(final String persistentKeepalive) {
-            this.persistentKeepalive = persistentKeepalive;
-            notifyPropertyChanged(BR.persistentKeepalive);
+        public Builder setPersistentKeepalive(final int persistentKeepalive) {
+            if (persistentKeepalive < 0 || persistentKeepalive > MAX_PERSISTENT_KEEPALIVE)
+                throw new IllegalArgumentException("Invalid value for PersistentKeepalive");
+            this.persistentKeepalive = persistentKeepalive == 0 ?
+                    Optional.empty() : Optional.of(persistentKeepalive);
+            return this;
         }
 
-        public void setPreSharedKey(final String preSharedKey) {
-            this.preSharedKey = preSharedKey;
-            notifyPropertyChanged(BR.preSharedKey);
+        public Builder setPreSharedKey(final Key preSharedKey) {
+            this.preSharedKey = Optional.of(preSharedKey);
+            return this;
         }
 
-        public void setPublicKey(final String publicKey) {
+        public Builder setPublicKey(final Key publicKey) {
             this.publicKey = publicKey;
-            notifyPropertyChanged(BR.publicKey);
-        }
-
-        public void toggleExcludePrivateIPs() {
-            final Collection<String> ips = new HashSet<>(Arrays.asList(Attribute.stringToList(allowedIPs)));
-            final boolean hasDefaultRoute = ips.contains(DEFAULT_ROUTE_V4);
-            final boolean hasDefaultRouteModRFC1918 = ips.containsAll(DEFAULT_ROUTE_MOD_RFC1918_V4);
-            if ((!hasDefaultRoute && !hasDefaultRouteModRFC1918) || numSiblings > 0)
-                return;
-            Iterables.removeIf(ips, ip -> !ip.contains(":"));
-            if (hasDefaultRoute) {
-                ips.addAll(DEFAULT_ROUTE_MOD_RFC1918_V4);
-                ips.addAll(interfaceDNSRoutes);
-            } else if (hasDefaultRouteModRFC1918)
-                ips.add(DEFAULT_ROUTE_V4);
-            setAllowedIPs(Attribute.iterableToString(ips));
-        }
-
-        @Override
-        public void writeToParcel(final Parcel dest, final int flags) {
-            dest.writeString(allowedIPs);
-            dest.writeString(endpoint);
-            dest.writeString(persistentKeepalive);
-            dest.writeString(preSharedKey);
-            dest.writeString(publicKey);
-            dest.writeInt(numSiblings);
-            dest.writeStringList(interfaceDNSRoutes);
+            return this;
         }
     }
 }
diff --git a/app/src/main/java/com/wireguard/crypto/Key.java b/app/src/main/java/com/wireguard/crypto/Key.java
new file mode 100644
index 00000000..85146794
--- /dev/null
+++ b/app/src/main/java/com/wireguard/crypto/Key.java
@@ -0,0 +1,255 @@
+/*
+ * Copyright © 2017-2018 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.crypto;
+
+import java.util.Arrays;
+
+/**
+ * Represents a WireGuard public or private key. This class uses specialized constant-time base64
+ * and hexadecimal codec implementations that resist side-channel attacks.
+ * <p>
+ * Instances of this class are immutable.
+ */
+@SuppressWarnings("MagicNumber")
+public final class Key {
+    private final byte[] key;
+
+    /**
+     * Constructs an object encapsulating the supplied key.
+     *
+     * @param key an array of bytes containing a binary key. Callers of this constructor are
+     *            responsible for ensuring that the array is of the correct length.
+     */
+    private Key(final byte[] key) {
+        // Defensively copy to ensure immutability.
+        this.key = Arrays.copyOf(key, key.length);
+    }
+
+    /**
+     * Decodes a single 4-character base64 chunk to an integer in constant time.
+     *
+     * @param src       an array of at least 4 characters in base64 format
+     * @param srcOffset the offset of the beginning of the chunk in {@code src}
+     * @return the decoded 3-byte integer, or some arbitrary integer value if the input was not
+     * valid base64
+     */
+    private static int decodeBase64(final char[] src, final int srcOffset) {
+        int val = 0;
+        for (int i = 0; i < 4; ++i) {
+            final char c = src[i + srcOffset];
+            val |= (-1
+                    + ((((('A' - 1) - c) & (c - ('Z' + 1))) >>> 8) & (c - 64))
+                    + ((((('a' - 1) - c) & (c - ('z' + 1))) >>> 8) & (c - 70))
+                    + ((((('0' - 1) - c) & (c - ('9' + 1))) >>> 8) & (c + 5))
+                    + ((((('+' - 1) - c) & (c - ('+' + 1))) >>> 8) & 63)
+                    + ((((('/' - 1) - c) & (c - ('/' + 1))) >>> 8) & 64)
+            ) << (18 - 6 * i);
+        }
+        return val;
+    }
+
+    /**
+     * Encodes a single 4-character base64 chunk from 3 consecutive bytes in constant time.
+     *
+     * @param src        an array of at least 3 bytes
+     * @param srcOffset  the offset of the beginning of the chunk in {@code src}
+     * @param dest       an array of at least 4 characters
+     * @param destOffset the offset of the beginning of the chunk in {@code dest}
+     */
+    private static void encodeBase64(final byte[] src, final int srcOffset,
+                                     final char[] dest, final int destOffset) {
+        final byte[] input = {
+                (byte) ((src[srcOffset] >>> 2) & 63),
+                (byte) ((src[srcOffset] << 4 | ((src[1 + srcOffset] & 0xff) >>> 4)) & 63),
+                (byte) ((src[1 + srcOffset] << 2 | ((src[2 + srcOffset] & 0xff) >>> 6)) & 63),
+                (byte) ((src[2 + srcOffset]) & 63),
+        };
+        for (int i = 0; i < 4; ++i) {
+            dest[i + destOffset] = (char) (input[i] + 'A'
+                    + (((25 - input[i]) >>> 8) & 6)
+                    - (((51 - input[i]) >>> 8) & 75)
+                    - (((61 - input[i]) >>> 8) & 15)
+                    + (((62 - input[i]) >>> 8) & 3));
+        }
+    }
+
+    /**
+     * Decodes a WireGuard public or private key from its base64 string representation. This
+     * function throws a {@link KeyFormatException} if the source string is not well-formed.
+     *
+     * @param str the base64 string representation of a WireGuard key
+     * @return the decoded key encapsulated in an immutable container
+     */
+    public static Key fromBase64(final String str) {
+        final char[] input = str.toCharArray();
+        if (input.length != Format.BASE64.length || input[Format.BASE64.length - 1] != '=')
+            throw new KeyFormatException(Format.BASE64);
+        final byte[] key = new byte[Format.BINARY.length];
+        int i;
+        int ret = 0;
+        for (i = 0; i < key.length / 3; ++i) {
+            final int val = decodeBase64(input, i * 4);
+            ret |= val >>> 31;
+            key[i * 3] = (byte) ((val >>> 16) & 0xff);
+            key[i * 3 + 1] = (byte) ((val >>> 8) & 0xff);
+            key[i * 3 + 2] = (byte) (val & 0xff);
+        }
+        final char[] endSegment = {
+                input[i * 4],
+                input[i * 4 + 1],
+                input[i * 4 + 2],
+                'A',
+        };
+        final int val = decodeBase64(endSegment, 0);
+        ret |= (val >>> 31) | (val & 0xff);
+        key[i * 3] = (byte) ((val >>> 16) & 0xff);
+        key[i * 3 + 1] = (byte) ((val >>> 8) & 0xff);
+
+        if (ret != 0)
+            throw new KeyFormatException(Format.BASE64);
+        return new Key(key);
+    }
+
+    /**
+     * Wraps a WireGuard public or private key in an immutable container. This function throws a
+     * {@link KeyFormatException} if the source data is not the correct length.
+     *
+     * @param bytes an array of bytes containing a WireGuard key in binary format
+     * @return the key encapsulated in an immutable container
+     */
+    public static Key fromBytes(final byte[] bytes) {
+        if (bytes.length != Format.BINARY.length)
+            throw new KeyFormatException(Format.BINARY);
+        return new Key(bytes);
+    }
+
+    /**
+     * Decodes a WireGuard public or private key from its hexadecimal string representation. This
+     * function throws a {@link KeyFormatException} if the source string is not well-formed.
+     *
+     * @param str the hexadecimal string representation of a WireGuard key
+     * @return the decoded key encapsulated in an immutable container
+     */
+    public static Key fromHex(final String str) {
+        final char[] input = str.toCharArray();
+        if (input.length != Format.HEX.length)
+            throw new KeyFormatException(Format.HEX);
+        final byte[] key = new byte[Format.BINARY.length];
+        int ret = 0;
+        for (int i = 0; i < key.length; ++i) {
+            int c;
+            int cNum;
+            int cNum0;
+            int cAlpha;
+            int cAlpha0;
+            int cVal;
+            final int cAcc;
+
+            c = input[i * 2];
+            cNum = c ^ 48;
+            cNum0 = ((cNum - 10) >>> 8) & 0xff;
+            cAlpha = (c & ~32) - 55;
+            cAlpha0 = (((cAlpha - 10) ^ (cAlpha - 16)) >>> 8) & 0xff;
+            ret |= ((cNum0 | cAlpha0) - 1) >>> 8;
+            cVal = (cNum0 & cNum) | (cAlpha0 & cAlpha);
+            cAcc = cVal * 16;
+
+            c = input[i * 2 + 1];
+            cNum = c ^ 48;
+            cNum0 = ((cNum - 10) >>> 8) & 0xff;
+            cAlpha = (c & ~32) - 55;
+            cAlpha0 = (((cAlpha - 10) ^ (cAlpha - 16)) >>> 8) & 0xff;
+            ret |= ((cNum0 | cAlpha0) - 1) >>> 8;
+            cVal = (cNum0 & cNum) | (cAlpha0 & cAlpha);
+            key[i] = (byte) (cAcc | cVal);
+        }
+        if (ret != 0)
+            throw new KeyFormatException(Format.HEX);
+        return new Key(key);
+    }
+
+    /**
+     * Returns the key as an array of bytes.
+     *
+     * @return an array of bytes containing the raw binary key
+     */
+    public byte[] getBytes() {
+        // Defensively copy to ensure immutability.
+        return Arrays.copyOf(key, key.length);
+    }
+
+    /**
+     * Encodes the key to base64.
+     *
+     * @return a string containing the encoded key
+     */
+    public String toBase64() {
+        final char[] output = new char[Format.BASE64.length];
+        int i;
+        for (i = 0; i < key.length / 3; ++i)
+            encodeBase64(key, i * 3, output, i * 4);
+        final byte[] endSegment = {
+                key[i * 3],
+                key[i * 3 + 1],
+                0,
+        };
+        encodeBase64(endSegment, 0, output, i * 4);
+        output[Format.BASE64.length - 1] = '=';
+        return new String(output);
+    }
+
+    /**
+     * Encodes the key to hexadecimal ASCII characters.
+     *
+     * @return a string containing the encoded key
+     */
+    public String toHex() {
+        final char[] output = new char[Format.HEX.length];
+        for (int i = 0; i < key.length; ++i) {
+            output[i * 2] = (char) (87 + (key[i] >> 4 & 0xf)
+                    + ((((key[i] >> 4 & 0xf) - 10) >> 8) & ~38));
+            output[i * 2 + 1] = (char) (87 + (key[i] & 0xf)
+                    + ((((key[i] & 0xf) - 10) >> 8) & ~38));
+        }
+        return new String(output);
+    }
+
+    /**
+     * The supported formats for encoding a WireGuard key.
+     */
+    public enum Format {
+        BASE64(44),
+        BINARY(32),
+        HEX(64);
+
+        private final int length;
+
+        Format(final int length) {
+            this.length = length;
+        }
+
+        public int getLength() {
+            return length;
+        }
+    }
+
+    /**
+     * An exception thrown when attempting to parse an invalid key (too short, too long, or byte
+     * data inappropriate for the format). The format being parsed can be accessed with the
+     * {@link #getFormat} method.
+     */
+    public static final class KeyFormatException extends RuntimeException {
+        private final Format format;
+
+        private KeyFormatException(final Format format) {
+            this.format = format;
+        }
+
+        public Format getFormat() {
+            return format;
+        }
+    }
+}
diff --git a/app/src/main/java/com/wireguard/crypto/KeyEncoding.java b/app/src/main/java/com/wireguard/crypto/KeyEncoding.java
deleted file mode 100644
index d29c2d44..00000000
--- a/app/src/main/java/com/wireguard/crypto/KeyEncoding.java
+++ /dev/null
@@ -1,161 +0,0 @@
-/*
- * Copyright © 2017-2018 WireGuard LLC. All Rights Reserved.
- * SPDX-License-Identifier: Apache-2.0
- */
-
-package com.wireguard.crypto;
-
-import com.wireguard.android.Application;
-import com.wireguard.android.R;
-
-/**
- * This is a specialized constant-time base64 and hex implementation that resists side-channel attacks.
- */
-
-@SuppressWarnings("MagicNumber")
-public final class KeyEncoding {
-    public static final int KEY_LENGTH = 32;
-    public static final int KEY_LENGTH_BASE64 = 44;
-    public static final int KEY_LENGTH_HEX = 64;
-    private static final String KEY_LENGTH_BASE64_EXCEPTION_MESSAGE =
-            Application.get().getString(R.string.key_length_base64_exception_message);
-    private static final String KEY_LENGTH_EXCEPTION_MESSAGE =
-            Application.get().getString(R.string.key_length_exception_message);
-    private static final String KEY_LENGTH_HEX_EXCEPTION_MESSAGE =
-            Application.get().getString(R.string.key_length_hex_exception_message);
-
-    private KeyEncoding() {
-        // Prevent instantiation.
-    }
-
-    private static int decodeBase64(final char[] src, final int srcOffset) {
-        int val = 0;
-        for (int i = 0; i < 4; ++i) {
-            final char c = src[i + srcOffset];
-            val |= (-1
-                    + ((((('A' - 1) - c) & (c - ('Z' + 1))) >>> 8) & (c - 64))
-                    + ((((('a' - 1) - c) & (c - ('z' + 1))) >>> 8) & (c - 70))
-                    + ((((('0' - 1) - c) & (c - ('9' + 1))) >>> 8) & (c + 5))
-                    + ((((('+' - 1) - c) & (c - ('+' + 1))) >>> 8) & 63)
-                    + ((((('/' - 1) - c) & (c - ('/' + 1))) >>> 8) & 64)
-            ) << (18 - 6 * i);
-        }
-        return val;
-    }
-
-    private static void encodeBase64(final byte[] src, final int srcOffset,
-                                     final char[] dest, final int destOffset) {
-        final byte[] input = {
-                (byte) ((src[srcOffset] >>> 2) & 63),
-                (byte) ((src[srcOffset] << 4 | ((src[1 + srcOffset] & 0xff) >>> 4)) & 63),
-                (byte) ((src[1 + srcOffset] << 2 | ((src[2 + srcOffset] & 0xff) >>> 6)) & 63),
-                (byte) ((src[2 + srcOffset]) & 63),
-        };
-        for (int i = 0; i < 4; ++i) {
-            dest[i + destOffset] = (char) (input[i] + 'A'
-                    + (((25 - input[i]) >>> 8) & 6)
-                    - (((51 - input[i]) >>> 8) & 75)
-                    - (((61 - input[i]) >>> 8) & 15)
-                    + (((62 - input[i]) >>> 8) & 3));
-        }
-    }
-
-    public static byte[] keyFromBase64(final String str) {
-        final char[] input = str.toCharArray();
-        final byte[] key = new byte[KEY_LENGTH];
-        if (input.length != KEY_LENGTH_BASE64 || input[KEY_LENGTH_BASE64 - 1] != '=')
-            throw new IllegalArgumentException(KEY_LENGTH_BASE64_EXCEPTION_MESSAGE);
-        int i;
-        int ret = 0;
-        for (i = 0; i < KEY_LENGTH / 3; ++i) {
-            final int val = decodeBase64(input, i * 4);
-            ret |= val >>> 31;
-            key[i * 3] = (byte) ((val >>> 16) & 0xff);
-            key[i * 3 + 1] = (byte) ((val >>> 8) & 0xff);
-            key[i * 3 + 2] = (byte) (val & 0xff);
-        }
-        final char[] endSegment = {
-                input[i * 4],
-                input[i * 4 + 1],
-                input[i * 4 + 2],
-                'A',
-        };
-        final int val = decodeBase64(endSegment, 0);
-        ret |= (val >>> 31) | (val & 0xff);
-        key[i * 3] = (byte) ((val >>> 16) & 0xff);
-        key[i * 3 + 1] = (byte) ((val >>> 8) & 0xff);
-
-        if (ret != 0)
-            throw new IllegalArgumentException(KEY_LENGTH_BASE64_EXCEPTION_MESSAGE);
-        return key;
-    }
-
-    public static byte[] keyFromHex(final String str) {
-        final char[] input = str.toCharArray();
-        final byte[] key = new byte[KEY_LENGTH];
-        if (input.length != KEY_LENGTH_HEX)
-            throw new IllegalArgumentException(KEY_LENGTH_HEX_EXCEPTION_MESSAGE);
-        int ret = 0;
-
-        for (int i = 0; i < KEY_LENGTH_HEX; i += 2) {
-            int c;
-            int cNum;
-            int cNum0;
-            int cAlpha;
-            int cAlpha0;
-            int cVal;
-            final int cAcc;
-
-            c = input[i];
-            cNum = c ^ 48;
-            cNum0 = ((cNum - 10) >>> 8) & 0xff;
-            cAlpha = (c & ~32) - 55;
-            cAlpha0 = (((cAlpha - 10) ^ (cAlpha - 16)) >>> 8) & 0xff;
-            ret |= ((cNum0 | cAlpha0) - 1) >>> 8;
-            cVal = (cNum0 & cNum) | (cAlpha0 & cAlpha);
-            cAcc = cVal * 16;
-
-            c = input[i + 1];
-            cNum = c ^ 48;
-            cNum0 = ((cNum - 10) >>> 8) & 0xff;
-            cAlpha = (c & ~32) - 55;
-            cAlpha0 = (((cAlpha - 10) ^ (cAlpha - 16)) >>> 8) & 0xff;
-            ret |= ((cNum0 | cAlpha0) - 1) >>> 8;
-            cVal = (cNum0 & cNum) | (cAlpha0 & cAlpha);
-            key[i / 2] = (byte) (cAcc | cVal);
-        }
-        if (ret != 0)
-            throw new IllegalArgumentException(KEY_LENGTH_HEX_EXCEPTION_MESSAGE);
-        return key;
-    }
-
-    public static String keyToBase64(final byte[] key) {
-        final char[] output = new char[KEY_LENGTH_BASE64];
-        if (key.length != KEY_LENGTH)
-            throw new IllegalArgumentException(KEY_LENGTH_EXCEPTION_MESSAGE);
-        int i;
-        for (i = 0; i < KEY_LENGTH / 3; ++i)
-            encodeBase64(key, i * 3, output, i * 4);
-        final byte[] endSegment = {
-                key[i * 3],
-                key[i * 3 + 1],
-                0,
-        };
-        encodeBase64(endSegment, 0, output, i * 4);
-        output[KEY_LENGTH_BASE64 - 1] = '=';
-        return new String(output);
-    }
-
-    public static String keyToHex(final byte[] key) {
-        final char[] output = new char[KEY_LENGTH_HEX];
-        if (key.length != KEY_LENGTH)
-            throw new IllegalArgumentException(KEY_LENGTH_EXCEPTION_MESSAGE);
-        for (int i = 0; i < KEY_LENGTH; ++i) {
-            output[i * 2] = (char) (87 + (key[i] >> 4 & 0xf)
-                    + ((((key[i] >> 4 & 0xf) - 10) >> 8) & ~38));
-            output[i * 2 + 1] = (char) (87 + (key[i] & 0xf)
-                    + ((((key[i] & 0xf) - 10) >> 8) & ~38));
-        }
-        return new String(output);
-    }
-}
diff --git a/app/src/main/java/com/wireguard/crypto/KeyPair.java b/app/src/main/java/com/wireguard/crypto/KeyPair.java
new file mode 100644
index 00000000..2b2bf564
--- /dev/null
+++ b/app/src/main/java/com/wireguard/crypto/KeyPair.java
@@ -0,0 +1,81 @@
+/*
+ * Copyright © 2017-2018 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.crypto;
+
+import java.security.SecureRandom;
+
+/**
+ * Represents a Curve25519 key pair as used by WireGuard.
+ * <p>
+ * Instances of this class are immutable.
+ */
+public class KeyPair {
+    private final Key privateKey;
+    private final Key publicKey;
+
+    /**
+     * Creates a key pair using a newly-generated private key.
+     */
+    public KeyPair() {
+        this(generatePrivateKey());
+    }
+
+    /**
+     * Creates a key pair using an existing private key.
+     *
+     * @param privateKey a private key, used to derive the public key
+     */
+    public KeyPair(final Key privateKey) {
+        this.privateKey = privateKey;
+        publicKey = generatePublicKey(privateKey);
+    }
+
+    /**
+     * Generates a private key using the system's {@link SecureRandom} number generator.
+     *
+     * @return a well-formed random private key
+     */
+    @SuppressWarnings("MagicNumber")
+    private static Key generatePrivateKey() {
+        final SecureRandom secureRandom = new SecureRandom();
+        final byte[] privateKey = new byte[Key.Format.BINARY.getLength()];
+        secureRandom.nextBytes(privateKey);
+        privateKey[0] &= 248;
+        privateKey[31] &= 127;
+        privateKey[31] |= 64;
+        return Key.fromBytes(privateKey);
+    }
+
+    /**
+     * Generates a public key from an existing private key.
+     *
+     * @param privateKey a private key
+     * @return a well-formed public key that corresponds to the supplied private key
+     */
+    private static Key generatePublicKey(final Key privateKey) {
+        final byte[] publicKey = new byte[Key.Format.BINARY.getLength()];
+        Curve25519.eval(publicKey, 0, privateKey.getBytes(), null);
+        return Key.fromBytes(publicKey);
+    }
+
+    /**
+     * Returns the private key from the key pair.
+     *
+     * @return the private key
+     */
+    public Key getPrivateKey() {
+        return privateKey;
+    }
+
+    /**
+     * Returns the public key from the key pair.
+     *
+     * @return the public key
+     */
+    public Key getPublicKey() {
+        return publicKey;
+    }
+}
diff --git a/app/src/main/java/com/wireguard/crypto/Keypair.java b/app/src/main/java/com/wireguard/crypto/Keypair.java
deleted file mode 100644
index 0ee27542..00000000
--- a/app/src/main/java/com/wireguard/crypto/Keypair.java
+++ /dev/null
@@ -1,55 +0,0 @@
-/*
- * Copyright © 2017-2018 WireGuard LLC. All Rights Reserved.
- * SPDX-License-Identifier: Apache-2.0
- */
-
-package com.wireguard.crypto;
-
-import java.security.SecureRandom;
-
-/**
- * Represents a Curve25519 keypair as used by WireGuard.
- */
-
-public class Keypair {
-    private final byte[] privateKey;
-    private final byte[] publicKey;
-
-    public Keypair() {
-        this(generatePrivateKey());
-    }
-
-    private Keypair(final byte[] privateKey) {
-        this.privateKey = privateKey;
-        publicKey = generatePublicKey(privateKey);
-    }
-
-    public Keypair(final String privateKey) {
-        this(KeyEncoding.keyFromBase64(privateKey));
-    }
-
-    @SuppressWarnings("MagicNumber")
-    private static byte[] generatePrivateKey() {
-        final SecureRandom secureRandom = new SecureRandom();
-        final byte[] privateKey = new byte[KeyEncoding.KEY_LENGTH];
-        secureRandom.nextBytes(privateKey);
-        privateKey[0] &= 248;
-        privateKey[31] &= 127;
-        privateKey[31] |= 64;
-        return privateKey;
-    }
-
-    private static byte[] generatePublicKey(final byte[] privateKey) {
-        final byte[] publicKey = new byte[KeyEncoding.KEY_LENGTH];
-        Curve25519.eval(publicKey, 0, privateKey, null);
-        return publicKey;
-    }
-
-    public String getPrivateKey() {
-        return KeyEncoding.keyToBase64(privateKey);
-    }
-
-    public String getPublicKey() {
-        return KeyEncoding.keyToBase64(publicKey);
-    }
-}
diff --git a/app/src/main/res/layout/tunnel_detail_fragment.xml b/app/src/main/res/layout/tunnel_detail_fragment.xml
index 11cfafae..9b06ddd4 100644
--- a/app/src/main/res/layout/tunnel_detail_fragment.xml
+++ b/app/src/main/res/layout/tunnel_detail_fragment.xml
@@ -19,7 +19,7 @@
 
         <variable
             name="config"
-            type="com.wireguard.config.Config.Observable" />
+            type="com.wireguard.config.Config" />
     </data>
 
     <ScrollView
@@ -102,7 +102,7 @@
                         android:ellipsize="end"
                         android:maxLines="1"
                         android:onClick="@{ClipboardUtils::copyTextView}"
-                        android:text="@{config.interfaceSection.publicKey}" />
+                        android:text="@{config.interface.keyPair.publicKey.toBase64}" />
 
                     <TextView
                         android:id="@+id/addresses_label"
@@ -120,7 +120,7 @@
                         android:layout_height="wrap_content"
                         android:layout_below="@+id/addresses_label"
                         android:contentDescription="@string/addresses"
-                        android:text="@{config.interfaceSection.addresses}" />
+                        android:text="@{config.interface.addresses}" />
                 </RelativeLayout>
             </android.support.v7.widget.CardView>
 
diff --git a/app/src/main/res/layout/tunnel_detail_peer.xml b/app/src/main/res/layout/tunnel_detail_peer.xml
index 91be0011..767e0383 100644
--- a/app/src/main/res/layout/tunnel_detail_peer.xml
+++ b/app/src/main/res/layout/tunnel_detail_peer.xml
@@ -8,7 +8,7 @@
 
         <variable
             name="item"
-            type="com.wireguard.config.Peer.Observable" />
+            type="com.wireguard.config.Peer" />
     </data>
 
     <android.support.v7.widget.CardView
@@ -54,7 +54,7 @@
                 android:ellipsize="end"
                 android:maxLines="1"
                 android:onClick="@{ClipboardUtils::copyTextView}"
-                android:text="@{item.publicKey}" />
+                android:text="@{item.publicKey.toBase64}" />
 
             <TextView
                 android:id="@+id/allowed_ips_label"
@@ -71,7 +71,7 @@
                 android:layout_width="match_parent"
                 android:layout_height="wrap_content"
                 android:layout_below="@+id/allowed_ips_label"
-                android:text="@{item.allowedIPs}" />
+                android:text="@{item.allowedIps}" />
 
             <TextView
                 android:id="@+id/endpoint_label"
diff --git a/app/src/main/res/layout/tunnel_editor_fragment.xml b/app/src/main/res/layout/tunnel_editor_fragment.xml
index f7976459..3945fffc 100644
--- a/app/src/main/res/layout/tunnel_editor_fragment.xml
+++ b/app/src/main/res/layout/tunnel_editor_fragment.xml
@@ -11,15 +11,17 @@
 
         <import type="com.wireguard.android.widget.NameInputFilter" />
 
-        <import type="com.wireguard.config.Peer" />
-
         <variable
             name="fragment"
             type="com.wireguard.android.fragment.TunnelEditorFragment" />
 
         <variable
             name="config"
-            type="com.wireguard.config.Config.Observable" />
+            type="com.wireguard.android.viewmodel.ConfigProxy" />
+
+        <variable
+            name="name"
+            type="String" />
     </data>
 
     <android.support.design.widget.CoordinatorLayout
@@ -76,7 +78,7 @@
                             android:layout_height="wrap_content"
                             android:layout_below="@+id/interface_name_label"
                             android:inputType="textNoSuggestions|textVisiblePassword"
-                            android:text="@={config.name}"
+                            android:text="@={name}"
                             app:filter="@{NameInputFilter.newInstance()}" />
 
                         <TextView
@@ -96,7 +98,7 @@
                             android:layout_toStartOf="@+id/generate_private_key_button"
                             android:contentDescription="@string/public_key_description"
                             android:inputType="textNoSuggestions|textVisiblePassword"
-                            android:text="@={config.interfaceSection.privateKey}"
+                            android:text="@={config.interface.privateKey}"
                             app:filter="@{KeyInputFilter.newInstance()}" />
 
                         <Button
@@ -107,7 +109,7 @@
                             android:layout_alignBottom="@id/private_key_text"
                             android:layout_alignParentEnd="true"
                             android:layout_below="@+id/private_key_label"
-                            android:onClick="@{() -> config.interfaceSection.generateKeypair()}"
+                            android:onClick="@{() -> config.interface.generateKeyPair()}"
                             android:text="@string/generate" />
 
                         <TextView
@@ -130,7 +132,7 @@
                             android:hint="@string/hint_generated"
                             android:maxLines="1"
                             android:onClick="@{ClipboardUtils::copyTextView}"
-                            android:text="@{config.interfaceSection.publicKey}" />
+                            android:text="@{config.interface.publicKey}" />
 
                         <TextView
                             android:id="@+id/addresses_label"
@@ -150,7 +152,7 @@
                             android:layout_below="@+id/addresses_label"
                             android:layout_toStartOf="@+id/listen_port_text"
                             android:inputType="textNoSuggestions|textVisiblePassword"
-                            android:text="@={config.interfaceSection.addresses}" />
+                            android:text="@={config.interface.addresses}" />
 
                         <TextView
                             android:id="@+id/listen_port_label"
@@ -171,7 +173,7 @@
                             android:layout_alignStart="@+id/generate_private_key_button"
                             android:hint="@string/hint_random"
                             android:inputType="number"
-                            android:text="@={config.interfaceSection.listenPort}"
+                            android:text="@={config.interface.listenPort}"
                             android:textAlignment="center" />
 
                         <TextView
@@ -192,7 +194,7 @@
                             android:layout_below="@+id/dns_servers_label"
                             android:layout_toStartOf="@+id/mtu_text"
                             android:inputType="textNoSuggestions|textVisiblePassword"
-                            android:text="@={config.interfaceSection.dnses}" />
+                            android:text="@={config.interface.dnsServers}" />
 
                         <TextView
                             android:id="@+id/mtu_label"
@@ -213,7 +215,7 @@
                             android:layout_alignStart="@+id/generate_private_key_button"
                             android:hint="@string/hint_automatic"
                             android:inputType="number"
-                            android:text="@={config.interfaceSection.mtu}"
+                            android:text="@={config.interface.mtu}"
                             android:textAlignment="center" />
 
                         <Button
@@ -224,7 +226,7 @@
                             android:layout_below="@+id/dns_servers_text"
                             android:layout_marginLeft="-8dp"
                             android:onClick="@{fragment::onRequestSetExcludedApplications}"
-                            android:text="@{@plurals/set_excluded_applications(config.interfaceSection.excludedApplicationsCount, config.interfaceSection.excludedApplicationsCount)}" />
+                            android:text="@{@plurals/set_excluded_applications(config.interface.excludedApplications.size, config.interface.excludedApplications.size)}" />
                     </RelativeLayout>
                 </android.support.v7.widget.CardView>
 
@@ -244,7 +246,7 @@
                     android:layout_marginBottom="4dp"
                     android:layout_marginEnd="4dp"
                     android:layout_marginStart="4dp"
-                    android:onClick="@{() -> config.peers.add(Peer.Observable.newInstance())}"
+                    android:onClick="@{() -> config.addPeer()}"
                     android:text="@string/add_peer" />
             </LinearLayout>
         </ScrollView>
diff --git a/app/src/main/res/layout/tunnel_editor_peer.xml b/app/src/main/res/layout/tunnel_editor_peer.xml
index e270b71a..1224ddd3 100644
--- a/app/src/main/res/layout/tunnel_editor_peer.xml
+++ b/app/src/main/res/layout/tunnel_editor_peer.xml
@@ -10,11 +10,11 @@
 
         <variable
             name="collection"
-            type="android.databinding.ObservableList&lt;com.wireguard.config.Peer.Observable&gt;" />
+            type="android.databinding.ObservableList&lt;com.wireguard.android.viewmodel.PeerProxy&gt;" />
 
         <variable
             name="item"
-            type="com.wireguard.config.Peer.Observable" />
+            type="com.wireguard.android.viewmodel.PeerProxy" />
     </data>
 
     <android.support.v7.widget.CardView
@@ -52,7 +52,7 @@
                 android:layout_alignParentTop="true"
                 android:background="@null"
                 android:contentDescription="@string/delete"
-                android:onClick="@{() -> collection.remove(item)}"
+                android:onClick="@{() -> item.unbind()}"
                 android:src="@drawable/ic_action_delete" />
 
             <TextView
@@ -104,10 +104,9 @@
                 android:layout_height="wrap_content"
                 android:layout_alignBaseline="@+id/allowed_ips_label"
                 android:layout_alignParentEnd="true"
-                android:checked="@{item.isExcludePrivateIPsOn}"
-                android:onClick="@{() -> item.toggleExcludePrivateIPs()}"
+                android:checked="@={item.excludingPrivateIps}"
                 android:text="@string/exclude_private_ips"
-                android:visibility="@{item.canToggleExcludePrivateIPs ? View.VISIBLE : View.GONE}" />
+                android:visibility="@{item.ableToExcludePrivateIps ? View.VISIBLE : View.GONE}" />
 
             <EditText
                 android:id="@+id/allowed_ips_text"
@@ -115,7 +114,7 @@
                 android:layout_height="wrap_content"
                 android:layout_below="@+id/allowed_ips_label"
                 android:inputType="textNoSuggestions|textVisiblePassword"
-                android:text="@={item.allowedIPs}" />
+                android:text="@={item.allowedIps}" />
 
             <TextView
                 android:id="@+id/endpoint_label"
diff --git a/app/src/main/res/layout/tunnel_list_fragment.xml b/app/src/main/res/layout/tunnel_list_fragment.xml
index ccc1c5ae..d255005a 100644
--- a/app/src/main/res/layout/tunnel_list_fragment.xml
+++ b/app/src/main/res/layout/tunnel_list_fragment.xml
@@ -84,7 +84,7 @@
                 app:srcCompat="@drawable/ic_action_open_white" />
 
             <com.wireguard.android.widget.fab.LabeledFloatingActionButton
-                android:id="@+id/scan_qr_code"
+                android:id="@+id/create_from_qrcode"
                 android:layout_width="wrap_content"
                 android:layout_height="wrap_content"
                 android:onClick="@{fragment::onRequestScanQRCode}"
@@ -101,6 +101,5 @@
                 app:fab_title="@string/create_empty"
                 app:srcCompat="@drawable/ic_action_edit_white" />
         </com.wireguard.android.widget.fab.FloatingActionsMenu>
-
     </android.support.design.widget.CoordinatorLayout>
 </layout>
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 87ea18f5..6202ee78 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -63,6 +63,7 @@
     <string name="log_export_summary">Log file will be saved to downloads folder</string>
     <string name="mtu">MTU</string>
     <string name="name">Name</string>
+    <string name="parse_error">Cannot parse “%s” at %s</string>
     <string name="peer">Peer</string>
     <string name="permission_label">control WireGuard tunnels</string>
     <string name="permission_description">Allows an app to control WireGuard tunnels. Apps with this permission may enable and disable WireGuard tunnels at will, potentially misdirecting Internet traffic.</string>
@@ -99,13 +100,9 @@
     <string name="tunnel_rename_success">Successfully renamed tunnel to “%s”</string>
     <string name="tunnel_error_invalid_name">Invalid name</string>
     <string name="tunnel_error_already_exists">Tunnel %s already exists</string>
-    <string name="tunnel_error_empty_inetaddress">Empty address</string>
     <string name="tunnel_error_empty_interface_address">Address is empty</string>
-    <string name="tunnel_error_interface_parse_failed">Unable to parse line: “%s”</string>
     <string name="tunnel_error_forbidden_endpoint_chars">Forbidden characters in endpoint</string>
     <string name="tunnel_error_empty_peer_public_key">Peer public key may not be empty</string>
-    <string name="tunnel_error_invalid_config_line">Invalid configuration line: %s</string>
-    <string name="tunnel_error_no_config_information">Could not find any config information</string>
     <string name="key_length_base64_exception_message">WireGuard base64 keys must be 44 characters encoding 32 bytes</string>
     <string name="key_length_exception_message">WireGuard keys must be 32 bytes</string>
     <string name="key_length_hex_exception_message">WireGuard hex keys must be 64 characters encoding 32 bytes</string>
diff --git a/build.gradle b/build.gradle
index 68038e2a..421858de 100644
--- a/build.gradle
+++ b/build.gradle
@@ -7,7 +7,7 @@ allprojects {
 
 buildscript {
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.2.0'
+        classpath 'com.android.tools.build:gradle:3.2.1'
     }
     repositories {
         google()