ietf-openpgp
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Re: Back-signatures proposal

2003-10-28 15:29:53

On Tue, Oct 28, 2003 at 04:56:18PM -0500, Michael Young wrote:

I like the general proposal, for all of the reasons that David
listed.

My only question is about the encoding of the cross-signature
subpacket contents.  It could be anything from:
     a full Signature packet (including packet header); to,
     just the Signature packet contents; to,
     a leaner form with just the required fields (hash algorithm
      and signature MPIs), with the rest being assumed for the
      hash computation in order to reuse that.

I could live with any of these, but I lean toward the middle one.

As do I, for reasons given below, as well as for reasons of
simplicity.

If we do use a regular Signature packet (with or without header),
then I'd like to see a recommendation on what subpackets it should
contain.  The usual rules don't apply: for example, the issuer is
known.  I don't see a *need* for any subpackets, even creation time
(but I'm open to arguments).

I think it really depends on what the signature-in-a-subpacket is
being used for.  For the back-signature, it probably doesn't need any
subpackets.  At the same time, it doesn't hurt to include them.  Does
it matter very much?

I'd like to see the signature-in-a-subpacket used for other things
like notary signatures.  For that usage, the issuer and timestamp is
relevant.

David