On Mon, 23 Jul 2018 at 14:48, Sitaram Chamarty <sitaramc@xxxxxxxxx> wrote: > On 07/23/2018 06:10 PM, demerphq wrote: > > On Sun, 22 Jul 2018 at 01:59, brian m. carlson > > <sandals@xxxxxxxxxxxxxxxxxxxx> wrote: > >> I will admit that I don't love making this decision by myself, because > >> right now, whatever I pick, somebody is going to be unhappy. I want to > >> state, unambiguously, that I'm trying to make a decision that is in the > >> interests of the Git Project, the community, and our users. > >> > >> I'm happy to wait a few more days to see if a consensus develops; if so, > >> I'll follow it. If we haven't come to one by, say, Wednesday, I'll make > >> a decision and write my patches accordingly. The community is free, as > >> always, to reject my patches if taking them is not in the interest of > >> the project. > > > > Hi Brian. > > > > I do not envy you this decision. > > > > Personally I would aim towards pushing this decision out to the git > > user base and facilitating things so we can choose whatever hash > > function (and config) we wish, including ones not invented yet. > > > > Failing that I would aim towards a hashing strategy which has the most > > flexibility. Keccak for instance has the interesting property that its > > security level is tunable, and that it can produce aribitrarily long > > hashes. Leaving aside other concerns raised elsewhere in this thread, > > these two features alone seem to make it a superior choice for an > > initial implementation. You can find bugs by selecting unusual hash > > sizes, including very long ones, and you can provide ways to tune the > > function to peoples security and speed preferences. Someone really > > paranoid can specify an unusually large round count and a very long > > hash. > > > > Also frankly I keep thinking that the ability to arbitrarily extend > > the hash size has to be useful /somewhere/ in git. > > I would not suggest arbitrarily long hashes. Not only would it > complicate a lot of code, it is not clear that it has any real benefit. It has the benefit of armoring the code for the *next* hash change, and making it clear that such decisions are arbitrary and should not be depended on. > Plus, the code contortions required to support arbitrarily long hashes > would be more susceptible to potential bugs and exploits, simply by > being more complex code. Why take chances? I think the benefits would outweight the risks. > I would suggest (a) hash size of 256 bits and (b) choice of any hash > function that can produce such a hash. If people feel strongly that 256 > bits may also turn out to be too small (really?) then a choice of 256 or > 512, but not arbitrary sizes. I am aware of too many systems that cannot change their size and are locked into woefully bad decisions that were made long ago to buy this. Making it a per-repo option, would eliminate assumptions and make for a more secure and flexible tool. Anyway, I am not going to do the work so my opinion is worth the price of the paper I sent it on. :-) cheers, Yves -- perl -Mre=debug -e "/just|another|perl|hacker/"
