Date: Sat, 26 Sep 2015 02:07:30 +0200 From: magnum <john.magnum@...hmail.com> To: john-dev@...ts.openwall.com Subject: Re: Reverse steps for single round sha(sha-1, sha256/384/512) On 23/09/15 18:12, Aleksey Cherepanov wrote: > Recently Solar mentioned a macro with reverse of 3 rounds of SHA2, but > 7 rounds can be reversed. > > Below there is generic backward step for SHA2 as if it is last, next > can be obtained just decreasing "indexes", e.g. with the following > perl filter: perl -pe 's/([a-h]|i = )(\d+)/$1 . ($2 - 1)/ge' Thank's a lot Aleksey, this is now implemented for SHA-256. I presume we can do exactly the same thing for SHA-512 but as far as I can see it's not possible for SHA-224/384 because we have more unknown data for them (the current three steps of reversing seems to be about it). There was another boost of 3-4% as expected. I have yet to implement branch-less special functions for this but I will eventually do so (actually there is yet another branch now, for reversing of SHA-256 vs. SHA-224). As of now we probably have a slight regression for iterated formats like PBKDF2 (I did not even check yet). magnum
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