Re: [openpgp] AEAD Chunk Size

Bart Butler <> Thu, 18 April 2019 17:28 UTC

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Subject: Re: [openpgp] AEAD Chunk Size
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Hi all,

Jon and I got on the phone today and discussed the AEAD chunk situation a little more. The compromise we reached is:

(1) MUST support chunks up to and including 8KiB.
(2) SHOULD NOT emit chunks larger than 8KiB.
(3) SHOULD reject chunks larger than 8KiB.

Jon likes this because it doesn't fully shut the door on experimentation. I like this because it strengthens the norm and puts the burden of justification for violating the norm on the person asking for huge chunks rather than the implementer. I expect (though please correct me if not) that Derek, Neil, and others working on embedded or otherwise constrained system will like this because the normative limit is low enough for most embedded/constrained systems to do streaming when incremental no-release semantics are desired. And I hope Werner likes this because GnuPG is already doing 8KiB chunks, so the work involved in changing GnuPG's implementation should be minimal :)

Does anyone have any objections to or comments regarding this language?