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Re: [Cfrg] AEAD outputs and RFC 7539 (ChaCha20-Poly1305)

Russ Housley <housley@vigilsec.com> Wed, 25 May 2016 22:22 UTC

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From: Russ Housley <housley@vigilsec.com>
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To: Martin Thomson <martin.thomson@gmail.com>
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Subject: Re: [Cfrg] AEAD outputs and RFC 7539 (ChaCha20-Poly1305)
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On May 24, 2016, at 2:02 AM, Yoav Nir <ynir.ietf@gmail.com> wrote:

> 
>> On 24 May 2016, at 2:57 AM, Martin Thomson <martin.thomson@gmail.com> wrote:
>> 
>> On 23 May 2016 at 19:36, Adam Langley <agl@imperialviolet.org> wrote:
>>> I favour the model of RFC5116, but it's not universal. There are
>>> certainly cases where the separate parts are used, for example when
>>> encrypting in place and storing tags out of band.
>> 
>> 
>> I'm sure those people with special needs can use special tools.  The
>> only reason I point this out is that it makes it harder to point at
>> ChaCha... as an AEAD.
> 
> Seems right. Perhaps the report should say:
> 
> OLD:
>  The output from the AEAD is twofold:
> 
> New:
>  The output from the AEAD is a concatenation of two parts:

That makes sense to me.

Russ

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