- markus@cvs.openbsd.org 2013/12/06 13:34:54

     [authfile.c authfile.h cipher.c cipher.h key.c packet.c ssh-agent.c]
     [ssh-keygen.c PROTOCOL.key] new private key format, bcrypt as KDF by
     default; details in PROTOCOL.key; feedback and lots help from djm;
     ok djm@

1 files changed, 68 insertions, 0 deletions

diff --git a/PROTOCOL.key b/PROTOCOL.key
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index 000000000..959bd7aee
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+++ b/PROTOCOL.key
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+This document describes the private key format for OpenSSH.
+
+1. Overall format
+
+The key consists of a header, a list of public keys, and
+an encrypted list of matching private keys.
+
+#define AUTH_MAGIC      "openssh-key-v1"
+
+        byte[]  AUTH_MAGIC
+        string  ciphername
+        string  kdfname
+        string  kdfoptions
+        int     number of keys N
+        string  publickey1
+        string  publickey2
+        ...
+        string  publickeyN
+        string  encrypted, padded list of private keys
+
+2. KDF options for kdfname "bcrypt"
+
+The options:
+
+        string salt
+        uint32 rounds
+
+are concatenated and represented as a string.
+
+3. Unencrypted list of N private keys
+
+The list of privatekey/comment pairs is padded with the
+bytes 1, 2, 3, ... until the total length is a multiple
+of the cipher block size.
+
+        uint32  checkint
+        uint32  checkint
+        string  privatekey1
+        string  comment1
+        string  privatekey2
+        string  comment2
+        ...
+        string  privatekeyN
+        string  commentN
+        char    1
+        char    2
+        char    3
+        ...
+        char    padlen % 255
+
+Before the key is encrypted, a random integer is assigned
+to both checkint fields so successful decryption can be
+quickly checked by verifying that both checkint fields
+hold the same value.
+
+4. Encryption
+
+The KDF is used to derive a key, IV (and other values required by
+the cipher) from the passphrase. These values are then used to
+encrypt the unencrypted list of private keys.
+
+5. No encryption
+
+For unencrypted keys the cipher "none" and the KDF "none"
+are used with empty passphrases. The options if the KDF "none"
+are the empty string.
+
+$OpenBSD: PROTOCOL.key,v 1.1 2013/12/06 13:34:54 markus Exp $