Re: [openpgp] Fingerprints and their collisions resistance

[ianG <[e-mail]>]

On 3/01/13 19:17 PM, Jon Callas wrote:
> The proposal that we had a long time ago which was essentially prefix a hash with an algorithm number was a good one. I remember everyone thinking it was a good idea and no one belling the cat. I vaguely remember someone writing up an I-D on it, too.
>
> That's the way I'd go, as it's future-proofed.


If we have to have hash agility, I agree that's a good way to do it.

Alternatively we can do OIDs in which case we will generate arguments, 
external dependencies and work for ourselves for generations -- over on 
another list some were arguing recently about whether Taiwan was allowed 
to use this OID or that OID for their root key, Taiwan being one of 
those not-a-countries, and everyone arguing being not-those-authorities.

Hence my earlier question - has anyone allocated the OpenPGP numbers for 
Keccak as yet?  The reason I asked is because I stumbled on the code 
last week and thought what a fine idea it would be to at least prepare 
the way....  Strawman?

   SHA3-224         4        12
   SHA3-256         5        13
   SHA3-384         6        14
   SHA3-512         7        15

Strawman?  I'm not sure why there is a gap 4-7 in rfc4880.  Are there 
any spots already allocated?



Another question, back on the fingerprints.  If we end up doing a 
hash-agile fingerprint, how does the algorithm number get laid out by 
the users on their business cards?

E.g., can we agree on a one byte number, values 0 to 7F, with leading 
bit reserved for future escape valve?

Then, if it is to be written out, this would mean a "new-style 
fingerprint" is always an odd number of bytes.  Could we agree on a 
stylistic convention?  Something like:

   7F-- AB01 CD23 EF45 ...

Just thinking aloud.  Are there any other practical ramifications of 
going to an agile fingerprint?

iang