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Date: Mon, 9 Sep 2019 08:09:12 +0200
From: magnum <john.magnum@...hmail.com>
To: john-users@...ts.openwall.com
Subject: Re: SHA256(XOR(salt+pass, key))

On 2019-09-07 15:05, Marcin Gębarowski wrote:
> Looking for help with using john to crack the hashes I got, the 
> application creates them as follows:
> 
> SHA256(XOR(salt + pass, key))
> 
> 
> Salt and key are both 32 bytes long. I have the key. Hashes are stored 
> in format:
> base64(salt + hash)
> but I can easily change that to anything else.
> 
> 
> The main problem I'm having is the XOR function, which I was unable to 
> find in dynamic scripts library. Having something like:
> sha256(xor($s.$p, $key))
> as dynamic script would definitely solve this...

So is key like a 2nd (fixed) salt (pepper)? What application is that? 
I'm sure Jim could add XOR to dynamic compiler format with ease. Can you 
post a sample or two with known pass and key that we can use as test 
vectors?

There's a minor optimization possible - we could save state of SHA256 
after the first 8 rounds with a given salt, and reuse that for as many 
password candidates we like.

magnum

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