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Re: [openpgp] AEAD Chunk Size

Tobias Mueller <muelli@cryptobitch.de> Mon, 18 March 2019 09:49 UTC

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From: Tobias Mueller <muelli@cryptobitch.de>
To: "Neal H. Walfield" <neal@walfield.org>, openpgp@ietf.org
Date: Mon, 18 Mar 2019 10:49:22 +0100
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References: <87mumh33nc.wl-neal@walfield.org> <871s3qd4yg.fsf@wheatstone.g10code.de> <87mum6ekbd.wl-neal@walfield.org>
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Subject: Re: [openpgp] AEAD Chunk Size
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Hi,

On Thu, 2019-03-07 at 17:11 +0100, Neal H. Walfield wrote:
> > Let me repeat it again: The chunking was introduced for just one
> > purpose: To be able to detect rare transmission errors earlier than
> > at
> > the end of the message.
> 
> I agree that AEAD helps detect transmission errors earlier.  But, AEAD
> does so much more than that.  In particular, it prevents attacks like
> EFAIL.  It seems to me that it's worth adapting to this new threat.
I have the feeling that this is the spot where we are close to hitting
the underlying misunderstanding.

AFAICS, Werner is talking about chunking. You are talking about AEAD. I
have the feeling that it's helpful for the discussion to carefully
distinguish those.

You seem to imply that any chunked scheme is proper AEAD. But that's not
true. It's not difficult to make a scheme with chunks, and the spec
probably has already done so, but it's not trivial.

Cheers,
  Tobi

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