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/*
* 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;
}
}
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