On 12/09/2010 02:17 PM, Robert J. Hansen wrote: > IMO, quite high. If you use the same key material, then if the old > OpenPGP certificate format ever becomes weak an attacker can simply take > an old certificate of yours, upgrade it to the new format, and bang > they're off to the races.
Maybe we're not talking about the same thing, but i don't understand the attack you describe. Why would a weakness in the old certificate format would be able to invalidate the same key under a new format? Note: i am *not* talking about a weakness in the underlying ciphers, digests, or asymmetric algorithms involved. A weakness in the certificate format itself would certainly make me wary of relying on certificates in the weak format, but why would it mandate re-keying? Could you give a more detailed example of such an attack? > If/when the time comes for SHA-1 to be completely removed from OpenPGP, > the migration path will quite likely involve new keys -- the same way > that the V3/V4 migration path in the past necessitated new keys. Could you point to a reference that explains why a person with a v3 key considered sufficiently-strong by that day's estimation (say, 1024-bit RSA) would have had to create an entirely new key instead of just migrating their old key to v4? Thanks for clarifying, --dkg
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