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      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 	byte[]	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 1.4 2024/03/30 05:56:22 djm Exp $
     72