Re: [openpgp] Followup on fingerprints

Werner Koch <wk@gnupg.org> Wed, 29 July 2015 08:40 UTC

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From: Werner Koch <wk@gnupg.org>
To: Phillip Hallam-Baker <phill@hallambaker.com>
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In-Reply-To: <CAMm+LwgTcn8CY+Zk-f9gzXQtMJezG97T+kx2=C7PR5g7zFer_A@mail.gmail.com> (Phillip Hallam-Baker's message of "Tue, 28 Jul 2015 10:52:05 -0400")
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Subject: Re: [openpgp] Followup on fingerprints
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On Tue, 28 Jul 2015 16:52, phill@hallambaker.com said:

> * Contact some usability types to ask about usability and changing up the
> block sizes.

OpenPGP does not specify a user interface but the wire format.
Obviously we use the most compact format there which is the plain binary
format.  The questions are

  - Do we need to explicity indicate the fingerprinting scheme (SHA-1 or
    SHA-256, or whatever) in the binary represenation.
  
  - Do we need truncation and how do we indicate a fingerprint scheme
    then given that it can't be deduced from the length.

  - Should we bind a certain fingerprint scheme to a public key packet
    versions as we did in the past (v3 = MD5, v4 = SHA1, maybe v5 =
    SHA256 with keyid being the leftmost octets).  Or is it okay to
    allow for multipe fingerprint schemes for the same key.



Salam-Shalom,

   Werner

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