Date: Thu, 3 Sep 2015 03:40:41 +0300 From: Aleksey Cherepanov <lyosha@...nwall.com> To: john-dev@...ts.openwall.com Subject: Re: reverse of full sha1 and sha256 limb when hash and block are known On Thu, Sep 03, 2015 at 03:34:54AM +0300, Aleksey Cherepanov wrote: > Easy practical application > > Consider a hash sha256(sha256(...).sha256(...)), for instance > sha256(sha256($p).sha256($s)) > > sha256($p).sha256($s) produces exactly 1 block of message, so the > second block is 0x80, padding and constant length always. So we can > reverse the second block and check intermediate state computing only 1 > limb instead of 2. That's up to 50% higher speed (considering that we I meant 2x speed up. That's 100% higher speed. Sorry! -- Regards, Aleksey Cherepanov
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