Re: [openpgp] Proposal to include AEAD OCB mode to 4880bis

Werner Koch <> Fri, 27 October 2017 11:14 UTC

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From: Werner Koch <>
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Subject: Re: [openpgp] Proposal to include AEAD OCB mode to 4880bis
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On Fri, 27 Oct 2017 12:38, said:

> Don't add multiple algorithms unless there isn't a very good reason for
> it. Add one that is good for everything. Having a "may" algorithm only

There is a good reason for adding a MAY mode:

- We want an AEAD mode.
- The WG seems not to like OCB for political (patent) reasons.
- Thus the proposed solution is to require EAX but prepare for other
- OCB has been suggested as such another mode.
- We can add it to rfc4880bis as MAY mode to give a specification in
  case someone will implement it anyway.

Consider what will happen if we don't do this: OCB may be implemented
anyway but at best an I-D extending RFC4880bis is used as specification.
Or worse, there is no spec at all and everyone implements it in slightly
different ways.

Also: The first revisions of I-Ds for RFC6637 (ECC for OpenPGP)
specified _only_ NIST curves and didn't allowed for any other curves.
This has been challenged and fortunately RFC6637 allows for arbitrary
curves, albeit less well specified.  Without that semi-MAY we would not
have been able to deploy software using modern curves.  Patents on ECC
are still a minefield but nevertheless everyone is moving towards ECC.

> The GPG protocol is far more complex than it has to be.

You mean OpenPGP.



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