Re: [Cfrg] RGLC on draft-irtf-cfrg-chacha20-poly1305-01.txt

Yoav Nir <ynir.ietf@gmail.com> Sun, 12 October 2014 19:16 UTC

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To: Adam Langley <agl@imperialviolet.org>
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Date: Sun, 12 Oct 2014 22:16:10 +0300
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Subject: Re: [Cfrg] RGLC on draft-irtf-cfrg-chacha20-poly1305-01.txt
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Yes, and section 3.3 of RFC 5116 says so, so I can just point at that.

Yoav

-----Original Message-----
From: "Adam Langley" <agl@imperialviolet.org>
Sent: ‎10/‎12/‎2014 20:22
To: "Yoav Nir" <ynir.ietf@gmail.com>
Cc: "Dan Harkins" <dharkins@lounge.org>rg>; "cfrg@irtf.org" <cfrg@irtf.org>
Subject: Re: [Cfrg] RGLC on draft-irtf-cfrg-chacha20-poly1305-01.txt

On Sun, Oct 12, 2014 at 8:00 AM, Yoav Nir <ynir.ietf@gmail.com> wrote:
>>  It obviously takes AAD since section 2.8 mentions it as something to
>> include as input to AEAD_CHACHA20-POLY1305. So I'm suggesting you
>> define what AAD looks like when it is delivered to the mode: "Distinct
>> AAD shall be concatenated into a single input to
>> AEAD_CHACHA20-POLY1305", for example.
>
> OK. I’ll add a sentence like that.

Note that concatenating distinct AD inputs is not safe: ["a", "bc"] is
then ambiguous with ["ab", "c"]. Applications are free to use any
scheme they want, but concatenation shouldn't be implicitly endorsed.


Cheers

AGL

-- 
Adam Langley agl@imperialviolet.org https://www.imperialviolet.org