Date: Wed, 12 Aug 2015 16:57:36 -0500 From: JimF <jfoug@....net> To: john-dev@...ts.openwall.com Subject: Re: Formats using non-SIMD SHA2 implementations On Wed, 12 Aug 2015 16:42:24 -0500, magnum <john.magnum@...hmail.com> wrote: > On 2015-08-12 15:26, Lei Zhang wrote: >> Now I just finished episerver. I took a close look at the rest of the > ... >> - In clipperz, the salt has a maximum length of 128 byte, which is >> beyond the size of a single input block for SHA256. I've seen flags >> like SSEi_2BUF_INPUT and SSEi_4BUF_INPUT. I guess I'll have to >> quadruple the size the vector buffer to accommodate the salt ? > > Either that, or do it like in SAP G format (but that code is > unreadable). I never used SSEi_2/4BUF_INPUT but I'm sure Jim can provide > help if you get stuck. Clipperz was never done, because the hashing crypts are such a small part of the overall runtime. I did look at this a little this morning, and it appears that the hashing code may be up to 10% of the runtime. Most of the time is spent in the expmod, and that is not going to be optimized a whole lot better than with GMP. So I never deemed the ROI on put SIMD into the clean and easy to read code as being a priority. Also, at that time, I had limited experience doing multi-limb SIMD stuff. One key thing to keep in mind, is that having a mix of 1 and 2 limb crypts is not good. I do not know if this format could run into that situation, but likely it can. If you need any help with this format, I can certainly help out. NOTE, the first SRP done was wow-srp. It is very similar, but uses SHA1 as exponent setup. It was not done using SIMD either.
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