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Re: [openpgp] The combinatorial complexity of OpenPGPv4

Christoph Anton Mitterer <calestyo@scientia.net> Mon, 23 March 2015 18:48 UTC

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From: Christoph Anton Mitterer <calestyo@scientia.net>
To: openpgp@ietf.org
Date: Mon, 23 Mar 2015 19:48:28 +0100
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Subject: Re: [openpgp] The combinatorial complexity of OpenPGPv4
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On Tue, 2015-03-17 at 11:27 -0400, Derek Atkins wrote: 
> I don't agree with this statement.  It wasn't flexibility that stopped
> changing CFB, it was that CTR mode was relatively new when the group was
> working on 4880 (I'm not sure it even existed when we did 2440).  And
> compatibility was always (generally) paramount.  I.e., if it ain't
> completely broke let's not fix it..  and where it is broke, let's fix it
> in the most compatible way.
> 
> Were I do start from scratch today then yes, I'd just use GCM.  We could
> certainly add a GCM mode and a preference to specify support for it.
> But for interop I don't think we could drop CFB support completely from
> implementations.
Could you elaborate on that?

I probably lack some decent+recent cryptanalysis of CFB as used with
OpenPGP, but at least we had quite a number of crypto systems where it
caused all kinds of issues recently.

So *if* there's a new OpenPGP v.X (and not just "amendments" as with
Ed25519), shouldn't it be actually a goal to get current state of the
art things?


Cheers,
Chris.

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