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Re: [openpgp] v5 in the crypto-refresh draft

2021-06-05 12:56:35
On Sat 2021-06-05 12:22:38 +0000, Peter Gutmann wrote:
Daniel Kahn Gillmor <dkg(_at_)fifthhorseman(_dot_)net> writes:

Specific v5 changes

Another thing I'd like to see changed in v5 is the incredibly annoying way
OpenPGP handles its PRF.  For every PRF use on the planet except OpenPGP, you
specify the number of iterations of the PRF to be applied.  For OpenPGP you
specify the number of bytes to output and then have to work backwards through
the PRF to figure out how many iterations this amounts to.  Making things even
worse, the count is encoded in a weirdo fixed-point format that can't be
passed as an integer count parameter to anything because it's not, or
alternatively that if passed as an integer has to then be converted back into
its oddball fixed-point format when written.  So:

  Replace the S2K 'count' value with a 32-bit integer specifying the number of
  PRF iterations to apply.

I don't think the S2K updates for v5 have made it into the
crypto-refresh draft yet.  So i appreciate this comment but i hope we
can delay it until we address new forms of S2K (see e.g. commit
6337518cd35ee416129959982a10df85548b2117 in the step-by-step branch,
which is not yet merged).

    --dkg

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