Date: Mon, 31 Jan 2011 22:41:49 +0000 From: Freddie Witherden <freddie@...herden.org> To: john-users@...ts.openwall.com Subject: Re: FreeBSD crypt() / MD5-crypt implementation question On 31/01/11 22:04, Simon Marechal wrote: > Le 31/01/2011 16:32, Freddie Witherden a écrit : >> implementation is not ideal (I am reasonably confident that you can get >> 20% out of it without too much work) it does perform better than the > > That would be quite a nice improvement. The MD5 body function is pretty > tight (performs like barswf, and I know nothing that is faster), but the > "dispatch" part is far from optimal. According to my last profiling it > only accounted for 15% of the processing time. I'm not sure where the > low hanging fruits are in this patch ... Interesting, as I've found it to perform quite a bit worse than BarsWF. In the MD5 code I've been poking about with (which is--essentially--the same as that in JtR) around ~4% can be gained from 0 input optimisation for inputs less than 224-bits. This is similar to what BarsWF does, although far less aggressive, given that MD5 crypt strings tend to be longer. I've also had some luck changing the definitions of the F and G functions from their xor forms to their andnot forms. (Although this is quite likely to be dependant on the individual instruction latencies.) While I have not really toyed with the dispatch function I gleefully assumed after a cursory glance that with a bit of TLC a good few percent could be squeezed out of it. Perhaps I was being a bit too optimistic. Polemically yours, Freddie. Download attachment "signature.asc" of type "application/pgp-signature" (199 bytes)
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