Date: Mon, 22 Jun 2015 16:26:11 +0300 From: Aleksey Cherepanov <lyosha@...nwall.com> To: john-dev@...ts.openwall.com Subject: Re: bitslice SHA-256 Manually written bitslice is unbelievable! I did not look into code precisely, so the following may be implemented already. I propose a change: On Fri, May 29, 2015 at 06:35:29AM +0300, Solar Designer wrote: > "So we can expect that bitslice SHA256 will be (79-62)/62 = 27% slower > than normal SHA256" SHA-256 does on each step: h = g g = f f = e e = d + t1 d = c c = b b = a a = t1 + t2 I think 6 assignment may be replaced by an array and shifting pointer. Values in variables abcdefgh: abcdefgh - at the beginning of the first round, TabcDefg - at the beginning of the second round, where T = t1 + t2, D = d + t1 Let's shift it 1 char right: abcdefgh TabcDefg Now it looks like 6 variables were not moved. Let's introduce an array A. Then in code, replace variable 'a' with A, ..., 'h' with A[-7]. In the end of round, just do --A; . It needs more space for intermediate variables because array shifts one way, but I guess it is not a problem. Positions of variables in memory can be reversed to be hgfedcba to allow ++A; and positive indexes. It should remove 6 of 8 writes but add dereference op for all these variables. Is it worth? What do you think? Thanks! -- Regards, Aleksey Cherepanov
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