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Re: [openpgp] AEAD Chunk Size

"Neal H. Walfield" <neal@walfield.org> Wed, 13 March 2019 13:27 UTC

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Date: Wed, 13 Mar 2019 14:27:17 +0100
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From: "Neal H. Walfield" <neal@walfield.org>
To: Derek Atkins <derek@ihtfp.com>
Cc: Vincent Breitmoser <look@my.amazin.horse>, Werner Koch <wk@gnupg.org>, openpgp@ietf.org
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Subject: Re: [openpgp] AEAD Chunk Size
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On Wed, 13 Mar 2019 14:14:37 +0100,
Derek Atkins wrote:
> Vincent Breitmoser <look@my.amazin.horse> writes:
> 
> >> The chunking was introduced for just one purpose: To be able to detect rare
> >> transmission errors earlier than at the end of the message.
> >
> > ...really? All this is just to save a few cpu cycles in the rare cases of data
> > corruption that should have been handled by other layers (filesystem / transport
> > layer) in the first place? Why even bother?
> 
> No, it is more than that.  Imagine using OpenPGP to encrypt a full
> filesystem to tape backup.  You necessarily want to be able to chunk
> that as you are saving (and restoring).

I don't think Vincent is disputing the validity of Werner's use case
per se.  I think he is saying the marginal utility of that is tiny
(it's "just a performance improvement") relative to ciphertext
integrity (a security property).

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