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Date: Fri, 14 Aug 2015 10:35:19 +0800
From: Lei Zhang <>
Subject: Re: Formats using non-SIMD SHA2 implementations

> On Aug 13, 2015, at 5:42 AM, magnum <> wrote:
> On 2015-08-12 15:26, Lei Zhang wrote:
>> Now I just finished episerver. I took a close look at the rest of the formats in that list, and found a few 'technical' issues.
>> - For 7z, keepass and pdf, there's AES encryption involved at some step of hashing (and also RC4 in pdf). But so far we don't have a SIMD implementation of AES (or RC4). I'm not sure how to handle this.
> Just do in in scalar code (a loop) after running SIMD for producing the keys! For example, the sevenzip_decrypt() function probably needs no change (but if you change it, be sure not to break non-SIMD builds).

I traced the execution of 7z's encryption: the size the hashed message could be really big, far beyond even 4 SHA2 input blocks. I think it's not possible to do the hashing with a single call to SIMDSHA256body(). 

Is there a way to repeatedly invoking SIMDSHA256body() just like SHA256_Update()?


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