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Diffstat (limited to '')
| -rw-r--r-- | agent/ChangeLog | 4 | ||||
| -rw-r--r-- | agent/keyformat.txt | 138 |
2 files changed, 142 insertions, 0 deletions
diff --git a/agent/ChangeLog b/agent/ChangeLog index 288953dfd..3037e00f4 100644 --- a/agent/ChangeLog +++ b/agent/ChangeLog @@ -1,3 +1,7 @@ +2001-12-19 Werner Koch <[email protected]> + + * keyformat.txt: New. + 2001-12-19 Marcus Brinkmann <[email protected]> * query.c (start_pinentry): Add new argument to assuan_pipe_connect. diff --git a/agent/keyformat.txt b/agent/keyformat.txt new file mode 100644 index 000000000..dd34acc44 --- /dev/null +++ b/agent/keyformat.txt @@ -0,0 +1,138 @@ +keyformat.txt (wk 2001-12-18) +----------------------------- + + +Some notes on the format of the secret keys used with gpg-agent. + + +The secret[1] keys are store one per file in a directory below +the .gnupg homedirectory. This directory is named + + private-keys-v1.d + +and should have permissions 700. + +The secret keys are stored in files with a name matching the +hexadecimal representation of the keygrip[2]. The content of the file +is an S-Expression like tyhe ones used with Libgcrypt. Here is the +example of an unprotected file: + +(private-key + (rsa + (n #00e0ce9..[some bytes not shown]..51#) + (e #010001#) + (d #046129F..[some bytes not shown]..81#) + (p #00e861b..[some bytes not shown]..f1#) + (q #00f7a7c..[some bytes not shown]..61#) + (u #304559a..[some bytes not shown]..9b#) + ) +) + +Actually this form should not be used for regular purposes and only +accepted by gpg-agent with the configuration option: +--allow-non-canonical-key-format. + +The regular way to represent the keys is in canonical representation +with the additional requirement of an extra object around it[3]: + +(oid.1.3.6.1.4.1.11591.2.2.2 + (keyinfo human_readable_information_to_decribe_this_key) + (private-key + (rsa + (n #00e0ce9..[some bytes not shown]..51#) + (e #010001#) + (d #046129F..[some bytes not shown]..81#) + (p #00e861b..[some bytes not shown]..f1#) + (q #00f7a7c..[some bytes not shown]..61#) + (u #304559a..[some bytes not shown]..9b#) + ) + ) +) + + +This describes an unprotected key; a protected key is like this: + +(oid.1.3.6.1.4.1.11591.2.2.3 + (keyinfo human_readable_information_to_decribe_this_key) + (private-key + (rsa + (n #00e0ce9..[some bytes not shown]..51#) + (e #010001#) + (oid.1.3.6.1.4.1.11591.2.1.1.1 (parms) encrypted_octet_string) + ) + ) +) + +In this scheme the encrypted_octet_string is encrypted according to +the scheme identifier by the OID, most protection algorithms need +some parameters, which are given in a list before the +encrypted_octet_string. The result of the decryption process is a +list of the secret key parameters. + +Defined protection methods are: + +1.3.6.1.4.1.gnu(11591).aegypten(2) +.algorithms(1).keyprotection(1).s2k3-sha1-aes-cbc(1) + +This uses AES in CBS mode for encryption, SHA-1 fro integrity +protecion and the String to Key algorithm 3 from OpenPGP (rfc2440). + +Example: + +(oid.1.3.6.1.4.1.11591.2.1.1.1 + ((salt iterations) iv) + encrypted_octet_string +) + +The encrypted_octet string should yield this S-Exp (in canonical +representation) after decryption: + +(sha1_hash + (d #046129F..[some bytes not shown]..81#) + (p #00e861b..[some bytes not shown]..f1#) + (q #00f7a7c..[some bytes not shown]..61#) + (u #304559a..[some bytes not shown]..9b#) +) + +The first element is the SHA-1 hash calculated on the concatenation of the +public key and secret key parameter lists: i.e one has to hash the +concatenatiohn of these 6 canonical encoded lists for RSA, including +the parenthesis. + + (n #00e0ce9..[some bytes not shown]..51#) + (e #010001#) + (d #046129F..[some bytes not shown]..81#) + (p #00e861b..[some bytes not shown]..f1#) + (q #00f7a7c..[some bytes not shown]..61#) + (u #304559a..[some bytes not shown]..9b#) + + +After decryption the hash must be recalculated and compared against +the stored one - If they don't match the integrity of the key is not +given. + + + + + + + + + + + + + +Notes: + +[1] I usually use the terms private and secret key exchangeable but prefer the +term secret key because it can be visually be better distinguished +from the term public key. + +[2] The keygrip is a unique identifier for a key pair, it is +independent of any protocol, so that the same key can be ised with +different protocols. PKCS-15 calls this a subjectKeyHash; it can be +calculate using Libgcrypt's gcry_pk_get_keygrip(). + +[3] Even when canonical representation is required we will show the +S-expression here in a more readable representation.
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