DSA signature verification input
- by calccrypto
What is the data inputted into DSA when PGP signs a message? From RFC4880, i found
A Signature packet describes a binding between some public key and
some data. The most common signatures are a signature of a file or a block
of text, and a signature that is a certification of a User ID.
im not sure if it is the entire public key, just the public key packet, or some other derivative of a pgp key packet. whatever it is, i cannot get the DSA signature to verify
here is a sample im testing my program on:
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
abcd
-----BEGIN PGP SIGNATURE-----
Version: BCPG v1.39
iFkEARECABkFAk0z65ESHGFiYyAodGVzdCBrZXkpIDw+AAoJEC3Jkh8+bnkusO0A
oKG+HPF2Qrsth2zS9pK+eSCBSypOAKDBgC2Z0vf2EgLiiNMk8Bxpq68NkQ==
=gq0e
-----END PGP SIGNATURE-----
Dumped from pgpdump.net
Old: Signature Packet(tag 2)(89 bytes)
Ver 4 - new
Sig type - Signature of a canonical text document(0x01).
Pub alg - DSA Digital Signature Algorithm(pub 17)
Hash alg - SHA1(hash 2)
Hashed Sub: signature creation time(sub 2)(4 bytes)
Time - Mon Jan 17 07:11:13 UTC 2011
Hashed Sub: signer's User ID(sub 28)(17 bytes)
User ID - abc (test key) <>
Sub: issuer key ID(sub 16)(8 bytes)
Key ID - 0x2DC9921F3E6E792E
Hash left 2 bytes - b0 ed
DSA r(160 bits) - a1 be 1c f1 76 42 bb 2d 87 6c d2 f6 92 be 79 20 81 4b 2a 4e
DSA s(160 bits) - c1 80 2d 99 d2 f7 f6 12 02 e2 88 d3 24 f0 1c 69 ab af 0d 91
-> hash(DSA q bits)
and the public key for it is:
-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: BCPG v1.39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=CTgL
-----END PGP PUBLIC KEY BLOCK-----
the public key packet of the key is
mOIETTPqeBECALx+i9PIc4MB2DYXeqsWUav2cUtMU1N0inmFHSF/2x0d9IWEpVzEkRc30PvmEHI1faQi
t7NepnHkkphrXLAoZukAoNP3PB8NRQ6lRF6/6e8siUgJtmPLAf9IZOv4PI51gg6ICLKzNO9i3bcUx4ye
G2vjMOUAvsLkhSTWob0RxWppo6Pn6MOgdMQHIM5sDH0xGN0dOezzt/imAf9St2B0HQXVfAAbveXBeRoO
7jj/qcGx6hWmsKUrBVzdQhBk7Sku6C2KlMtkbtzd1fj8DtnrT8XOPKGp7/Y7ASzR
in radix 64
i have tried many different combinations of sha1(< some data + 'abcd'),but the calculated value v never equals r, of the signature
i know that the pgp implementation i used to create the key and signature is correct. i also know that my DSA implementation and PGP key data extraction program are correct. thus, the only thing left is the data to hash. what is the correct data to be hashed?
