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From:   "Jason A. Donenfeld" <Jason@zx2c4.com>
Date:   Thu, 12 Dec 2019 16:35:04 +0100
Message-ID: <CAHmME9rP_AAH6=R7ZRPnu3UPTvZ+c32-XYOr2jstSyQvCaQhnA@mail.gmail.com>
Subject: Re: [PATCH crypto-next v2 1/3] crypto: poly1305 - add new 32 and
 64-bit generic versions
To:     Martin Willi <martin@strongswan.org>
Cc:     Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Linux Crypto Mailing List <linux-crypto@vger.kernel.org>
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On Thu, Dec 12, 2019 at 4:30 PM Martin Willi <martin@strongswan.org> wrote:
> > The principle advantage of this patchset is the 64x64 code
>
> If there are platforms / code paths where this code matters, all fine.

It does matter.

>
> But the 64-bit version adds a lot of complexity because of the
> different state representation and the conversion between these states.
> I just don't think the gain (?) justifies that added complexity.

No, there's no conversion between the state representation, or any
complexity like that added.

I think if anything, the way this patch works, we wind up with
something easier to audit and look at. You can examine
poly1305-donna32.c and poly1305-donna64.c side-by-side and compare
line-by-line, as clean and isolate implementations. And this is very
well-known code too.