From: Joan Daemen Date: Fri, 29 Sep 2017 14:54:23 GMT Subject: Re: RFC v3: Another proposed hash function transition plan Message-ID: In-Reply-To: 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