Forging fingerprints/KeyID?

[Atom Smasher]

On Mon, 28 Nov 2005, David Shaw wrote:

> On Tue, Nov 29, 2005 at 05:36:38AM +0100, Christoph Anton Mitterer wrote:
>> Ah,.. tanks :-)
>> So it sould be completely enough to verify Name/eMail and the
>> Fingerprint when signing another key,... and I don't have to compare
>> creation date/keysize/algorithm/etc., right?
>
> Not unless you're signing a PGP 2.x (v3) key.
==================

how feasible would it be for an attacker to create a small (512 bit?) v4 
key with the same key id as a target key (irrelevant of the size and 
algorithm of the target key)?

it may not be practical today to do this with a fingerprint collision, but 
i subscribe to the theory that it doesn't hurt to check the size and 
algorithm of keys before signing them.


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