Re: [Sks-devel] about ECC and collisions

[Jean-Jacques Brucker]

Thanks for all.
I didn't know that fingerprint was calculated with a timestamp. Do you have any 
idea of the reason(s) to do that ?

(that change lot of things, and I'd also like to know if there is a way to 
query for specific keys).

(thanks for the link but i don't even know the difference between v3 and v4 
keys, is there a mechanism to avoid collisions in v4 ?
.... I have to RTFM.)

regards,
-- 
Jean-Jacques B.

Le lundi 4 avril 2011 19:20:01, Daniel Kahn Gillmor a écrit :
> On 04/04/2011 06:40 AM, Jean-Jacques Brucker wrote:
> > 1- As ECC crypto is soon available in gnupg, I am asking if sks key servers 
> > won't have problems managing them.
> > 
> > (That is  a great feature I am waiting for to use gpg with signing chains)
> > 
> > But the ECC curves are smaller than RSA or DSA keys, full collisions have 
> > more chances* to occurs (especially for NIST P-256).
> > (*note: maybe more that asteroid-human collisions :-) ). 
> 
> i'm pretty confused by this claim.  a collision in the fingerprint space
> would be pretty devastating to all OpenPGP implementations i know of,
> and the fingerprint space (160 bits) is significantly smaller than
> P-256.  I don't think an ECC key collision is worth worrying about.
> 
> > 2- I like to know how sks key servers manage 2 identical keys inside 
> > different certificates.
> > Is a warning sent to the owners of the same key ?
> 
> No SKS keyservers that i know of send any notifications to any
> keyholders.  If you want to be alerted about a change in your key, or
> the presence of other keys, you'll need do regular queries yourself.
> 
> I also don't know of any way that you can (via HKP) query an SKS
> keyserver for specific matches of key material.  You can query by user
> ID and by key fingerprint, but the key fingerprint is computed over a
> digest of a timestamp + the key material.  so it's possible to have two
> identical keys with different fingerprints.  this makes querying for
> specific keys difficult (though i'd be happy to learn that there was a
> way to do it).
> 
> > 3- When key ID collision occurs how to differentiate them with gnupg ? Is 
> > there a way to get only one of them from key servers (eg. for key ID 
> > A56E15A3, sorry if it's maybe not the place to ask that question).
> 
> The gnupg-specific part of this question is probably best asked on the
> gnupg-users list.  More generally, you might be interested in the
> discussion started recently by David Shaw on the IETF's OpenPGP WG
> mailing list:
> 
>  http://www.imc.org/ietf-openpgp/mail-archive/msg10684.html
> 
> the short version is: GnuPG's current implementation (as of 1.4.11 and
> 2.0.17) does not deal well with duplicate key IDs. :(
> 
> hth,
> 
>       --dkg
> 
>

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