ietf-openpgp
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I don't think that collides the way you think it does

2009-05-05 14:17:22

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Adi Shamir has pointed out for years now that no one has found *any*  
first or second preimage collision for SHA1. I'll shill for him here.

The new results for 2^52 work, assuming it's actually doable, are  
still for migrating a bitstring into two dependent bitstrings that  
collide. This has significance for people who run CAs with sequential  
serial numbers, or who want to tweak PDFs to project the future, or  
create binary distributions that have and do not have malware. It's  
serious *for* *those* *and* *similar* *cases*.

It does *not* mean that you can get a collision on an existing  
signature, nor on an existing fingerprint, nor on an MDC, etc. We are  
still sitting at *zero* first and second preimage collisions.

I think that we should push through the generic fingerprint proposal.  
I sorta-kinda picked up the ball on that to work with Derek, but if  
there's anyone else who wants it (or who wants to co-author with Derek  
and me), I'm happy to have less work to do.

I also think it's completely reasonable for an implementation to back  
away from SHA1 with all due speed -- but you're supposed to be doing  
that by 2010, anyway!

        Jon



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