Date: Sun, 5 Jul 2015 10:44:27 +0300 From: Solar Designer <solar@...nwall.com> To: john-dev@...ts.openwall.com Subject: Re: PHC: Lyra2 on GPU Agnieszka, On Sat, Jul 04, 2015 at 07:22:08PM +0300, Solar Designer wrote: > By the way, while your current choice of: > > > >> Speed for cost 1 (t) of 8, cost 2 (m) of 8, cost 3 (c) of 256, cost 4 (p) of 2 > > is fine for testing, I think for all of the PHC finalists we need to > tune parameters to a level comparable with defensive use of bcrypt at > cost 5, using this as our baseline. > > When used defensively and running an efficient implementation, bcrypt at > cost 5 achieves about 541*8 = ~4330 c/s on i7-4770K: > > solar@...l:~/crypt_blowfish-1.2-notest$ ./crypt_test_threads > 602.8 c/s real, 602.8 c/s virtual > 0: 540.4 c/s real > 1: 542.4 c/s real > 2: 542.4 c/s real > 3: 542.6 c/s real > 4: 540.4 c/s real > 5: 540.4 c/s real > 6: 542.4 c/s real > 7: 540.4 c/s real > > So you'd need to tune the PHC finalists to achieve the same defensive > use performance for their most optimal implementations on "well", and > these will be the settings you'd use for attacking them on GPU. You'd > set t_cost to the lowest supported value, parallelism to 1 (no thread > level parallelism within one instance), the rest of parameters as > recommended by the PHC finalist designers, and tune m_cost to achieve > the defensive speed above. Just to make it clear: this is important and high priority, for all of your PHC finalist formats. Also, please add an output line showing the per-instance memory size, as derived from the cost settings being benchmarked. E.g., this would have printed "192 KiB" (or the equivalent in bytes) for your Lyra2 benchmarks. > As an extra test, you'd set t_cost higher and m_cost lower, still for > the same defensive speed. But it's just an extra. The main test should > use the lowest supported t_cost. Alexander
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