PROTOCOL.key

   1 This document describes the private key format for OpenSSH.
   2
   3 1. Overall format
   4
   5 The key consists of a header, a list of public keys, and
   6 an encrypted list of matching private keys.
   7
   8 #define AUTH_MAGIC      "openssh-key-v1"
   9
  10         byte[]  AUTH_MAGIC
  11         string  ciphername
  12         string  kdfname
  13         string  kdfoptions
  14         uint32  number of keys N
  15         string  publickey1
  16         string  publickey2
  17         ...
  18         string  publickeyN
  19         string  encrypted, padded list of private keys
  20
  21 2. KDF options for kdfname "bcrypt"
  22
  23 The options:
  24
  25         string salt
  26         uint32 rounds
  27
  28 are concatenated and represented as a string.
  29
  30 3. Unencrypted list of N private keys
  31
  32 The list of privatekey/comment pairs is padded with the
  33 bytes 1, 2, 3, ... until the total length is a multiple
  34 of the cipher block size.
  35
  36         uint32  checkint
  37         uint32  checkint
  38         byte[]  privatekey1
  39         string  comment1
  40         byte[]  privatekey2
  41         string  comment2
  42         ...
  43         string  privatekeyN
  44         string  commentN
  45         byte    1
  46         byte    2
  47         byte    3
  48         ...
  49         byte    padlen % 255
  50
  51 where each private key is encoded using the same rules as used for
  52 SSH agent.
  53
  54 Before the key is encrypted, a random integer is assigned
  55 to both checkint fields so successful decryption can be
  56 quickly checked by verifying that both checkint fields
  57 hold the same value.
  58
  59 4. Encryption
  60
  61 The KDF is used to derive a key, IV (and other values required by
  62 the cipher) from the passphrase. These values are then used to
  63 encrypt the unencrypted list of private keys.
  64
  65 5. No encryption
  66
  67 For unencrypted keys the cipher "none" and the KDF "none"
  68 are used with empty passphrases. The options if the KDF "none"
  69 are the empty string.
  70
  71 $OpenBSD: PROTOCOL.key,v 1.3 2022/07/01 04:45:50 djm Exp $