Re: RFC v3: Another proposed hash function transition plan

[Joan Daemen <jda@noekeon.org>]

Dear Johannes,

if ever there was a SHA-2 competition, it must have been held inside 
NSA:-) But maybe you are confusing with the SHA-3 competition. In any 
case, when considering SHA-2 vs SHA-3 for usage in git, you may have a 
look at arguments we give in the following blogpost:

https://keccak.team/2017/open_source_crypto.html

Kind regards,

Joan Daemen

On 29/09/17 15:17, Johannes Schindelin wrote:
> Hi Gilles,
>
> On Tue, 19 Sep 2017, Gilles Van Assche wrote:
>
>> On 19/09/17 00:16, Johannes Schindelin wrote:
>>>>> SHA-256 got much more cryptanalysis than SHA3-256 […].
>>>> I do not think this is true.
>>> Please read what I said again: SHA-256 got much more cryptanalysis
>>> than SHA3-256.
>> Indeed. What I meant is that SHA3-256 got at least as much cryptanalysis
>> as SHA-256. :-)
> Oh? I got the opposite impression... I got the impression that *everybody*
> in the field banged on all the SHA-2 candidates because everybody was
> worried that SHA-1 would be utterly broken soon, and I got the impression
> that after this SHA-2 competition, people were less worried?
>
> Besides, I would expect that the difference in age (at *least* 7 years by
> my humble arithmetic skills) to make a difference...
>
>>> I never said that SHA3-256 got little cryptanalysis. Personally, I
>>> think that SHA3-256 got a ton more cryptanalysis than SHA-1, and that
>>> SHA-256 *still* got more cryptanalysis. But my opinion does not count,
>>> really. However, the two experts I pestered with questions over
>>> questions left me with that strong impression, and their opinion does
>>> count.
>> OK, I respect your opinion and that of your two experts. Yet, the "much
>> more" part of your statement, in particular, is something that may
>> require a bit more explanations.
> I would also like to point out the ubiquitousness of SHA-256. I have been
> asked to provide SHA-256 checksums for the downloads of Git for Windows,
> but not SHA3-256...
>
> And this is a practically-relevant thing: the more users of an algorithm
> there are, the more high-quality implementations you can choose from. And
> this becomes relevant, say, when you have to switch implementations due to
> license changes (*cough, cough looking in OpenSSL's direction*). Or when
> you have to support the biggest Git repository on this planet and have to
> eek out 5-10% more performance using the latest hardware. All of a sudden,
> your consideration cannot only be "security of the algorithm" any longer.
>
> Having said that, I am *really* happy to have SHA3-256 as a valid fallback
> option in case SHA-256 should be broken.
>
> Ciao,
> Johannes