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Re: [openpgp] AEAD Chunk Size

Jon Callas <joncallas@icloud.com> Tue, 02 April 2019 17:42 UTC

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From: Jon Callas <joncallas@icloud.com>
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Date: Tue, 02 Apr 2019 10:42:50 -0700
Cc: Jon Callas <joncallas@icloud.com>, Peter Gutmann <pgut001@cs.auckland.ac.nz>, "Neal H. Walfield" <neal@walfield.org>, "openpgp@ietf.org" <openpgp@ietf.org>, Justus Winter <justuswinter@gmail.com>
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To: "\"Conrado P. L. Gouvêa\"" <conradoplg@gmail.com>
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Subject: Re: [openpgp] AEAD Chunk Size
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> On Apr 2, 2019, at 6:12 AM, Conrado P. L. Gouvêa <conradoplg@gmail.com> wrote:
> 
> On Sat, Mar 30, 2019 at 11:59 PM Peter Gutmann
> <pgut001@cs.auckland.ac.nz> wrote:
>> I'm not saying remove it, just get some data to support making a decision in
>> some way.  In particular, AEAD is a good thing, but there's no evidence that
>> chunking with AEAD, which complicates things greatly, is useful or necessary.
>> 
> 
> I know you're tired of hearing about it... but EFail.
> Even if PGP used AEAD, but without chunks, EFail would probably still
> happen. If the AEAD data is arbitrarly large, then implementations
> would be forced to provide a streaming API that discloses
> unauthenticated plaintext, and the same thing would happen.

No, no, it’s okay, because this why I was saying, “Let’s not talk about Efail.” The AEAD discussion is good, and there are many reasons to upgrade to allow its use. If one of those reasons is complex, then having that be the major reason means that there’s a counter-argument that is essentially, “if this isn’t the silver bullet claimed, then maybe we shouldn’t do it,” and worse, it’s a completely reasonable counter-argument. 

There’s one more small issue around AEAD that I’ll bring up in another note.

	Jon

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