Re: [babel] Babel-MAC: Blake2s is 128-bits by default

Donald Eastlake <d3e3e3@gmail.com> Thu, 26 November 2020 19:03 UTC

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From: Donald Eastlake <d3e3e3@gmail.com>
Date: Thu, 26 Nov 2020 14:02:47 -0500
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To: Juliusz Chroboczek <jch@irif.fr>
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Subject: Re: [babel] Babel-MAC: Blake2s is 128-bits by default
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Hi Juliusz,

On Thu, Nov 26, 2020 at 7:04 AM Juliusz Chroboczek <jch@irif.fr> wrote:

> >> I do not believe that it impacts the security in any way (2^128 ns is
> >> roughly 10^12 times the age of the universe), but I could be wrong.
>
> > Yeah, makes sense, let's keep it at 32 bytes :)
>
> Excellent.  I'm therefore going to make the following change in AUTH48:
>
>   - in Section 4.1, replace
>
>    Every implementation MUST implement HMAC-SHA256 as defined in [RFC6234]
>    and Section 2 of [RFC2104], SHOULD implement keyed BLAKE2s [RFC7693],
>    and MAY implement other MAC algorithms.
>
>    Every implementation MUST implement HMAC-SHA256 as defined in [RFC6234]
>    and Section 2 of [RFC2104], SHOULD implement keyed BLAKE2s with 128-bit
>    (16-octet) digests [RFC7693], and MAY implement other MAC algorithms.
>
> I will not change the following text in Section 7:
>
>     Ideally, they should have a length of 32 octets (both for HMAC-SHA256
>     and Blake2s), and be chosen randomly.
>
> Donald, are you willing to call consensus on this point?
>

All this has been discussed on the WG mailing list with no objection and
there has been some further success but just to be sure, I'd like to wait a
couple of days before declaring consensus.

Thanks,
Donald
===============================
 Donald E. Eastlake 3rd   +1-508-333-2270 (cell)
 2386 Panoramic Circle, Apopka, FL 32703 USA
 d3e3e3@gmail.com


> -- Juliusz
>