V4 Key ID Mismatch - Check Me?

V Alex Brennen vab at cryptnet.net
Tue Jul 24 18:36:01 CEST 2001

On Tue, 24 Jul 2001, Justin Wienckowski wrote:

> For the life of me, I can't figure out why the key ID I compute
> (0A9A90AC3971FE26) doesn't match gpg's computed value.  To compute the
> key id, I'm doing the following:
> 1)  Hash the public key packet (tag 0x99, 2-octet length, 6-octet
> public key header, and the MPIs [mpi headers and data]) through SHA-1
> (using cryptlib's SHA1 stuff) 2)  Use low-order 64 bits of the hash
> value as the key id.

IIRC, you shouldn't hash the 0x99 and 2-octet length in with the
pubkey. (offset+3).

You may find an easier time looking at the keyserver code I wrote
which is simpler and more linear than the GnuPG code.

You can download the code here:


Make sure you get the snapshot and not the release.  There's been
allot of changes and improvements since the release.

	- VAB

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