diff options
Diffstat (limited to 'Documentation/device-mapper/dm-crypt.txt')
| -rw-r--r-- | Documentation/device-mapper/dm-crypt.txt | 53 |
1 files changed, 48 insertions, 5 deletions
diff --git a/Documentation/device-mapper/dm-crypt.txt b/Documentation/device-mapper/dm-crypt.txt index ff1f87bf26e8..3b3e1de21c9c 100644 --- a/Documentation/device-mapper/dm-crypt.txt +++ b/Documentation/device-mapper/dm-crypt.txt @@ -11,14 +11,31 @@ Parameters: <cipher> <key> <iv_offset> <device path> \ <offset> [<#opt_params> <opt_params>] <cipher> - Encryption cipher and an optional IV generation mode. - (In format cipher[:keycount]-chainmode-ivmode[:ivopts]). + Encryption cipher, encryption mode and Initial Vector (IV) generator. + + The cipher specifications format is: + cipher[:keycount]-chainmode-ivmode[:ivopts] Examples: - des aes-cbc-essiv:sha256 - twofish-ecb + aes-xts-plain64 + serpent-xts-plain64 + + Cipher format also supports direct specification with kernel crypt API + format (selected by capi: prefix). The IV specification is the same + as for the first format type. + This format is mainly used for specification of authenticated modes. - /proc/crypto contains supported crypto modes + The crypto API cipher specifications format is: + capi:cipher_api_spec-ivmode[:ivopts] + Examples: + capi:cbc(aes)-essiv:sha256 + capi:xts(aes)-plain64 + Examples of authenticated modes: + capi:gcm(aes)-random + capi:authenc(hmac(sha256),xts(aes))-random + capi:rfc7539(chacha20,poly1305)-random + + The /proc/crypto contains a list of curently loaded crypto modes. <key> Key used for encryption. It is encoded either as a hexadecimal number @@ -93,6 +110,32 @@ submit_from_crypt_cpus thread because it benefits CFQ to have writes submitted using the same context. +integrity:<bytes>:<type> + The device requires additional <bytes> metadata per-sector stored + in per-bio integrity structure. This metadata must by provided + by underlying dm-integrity target. + + The <type> can be "none" if metadata is used only for persistent IV. + + For Authenticated Encryption with Additional Data (AEAD) + the <type> is "aead". An AEAD mode additionally calculates and verifies + integrity for the encrypted device. The additional space is then + used for storing authentication tag (and persistent IV if needed). + +sector_size:<bytes> + Use <bytes> as the encryption unit instead of 512 bytes sectors. + This option can be in range 512 - 4096 bytes and must be power of two. + Virtual device will announce this size as a minimal IO and logical sector. + +iv_large_sectors + IV generators will use sector number counted in <sector_size> units + instead of default 512 bytes sectors. + + For example, if <sector_size> is 4096 bytes, plain64 IV for the second + sector will be 8 (without flag) and 1 if iv_large_sectors is present. + The <iv_offset> must be multiple of <sector_size> (in 512 bytes units) + if this flag is specified. + Example scripts =============== LUKS (Linux Unified Key Setup) is now the preferred way to set up disk |