phc-discussions - Re: [PHC] hash encryption

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20160324124741.GA10424@openwall.com>
Date: Thu, 24 Mar 2016 15:47:41 +0300
From: Solar Designer <solar@...nwall.com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] hash encryption

On Thu, Mar 24, 2016 at 03:29:34PM +0300, Solar Designer wrote:
> encoding the full length or full round+keylen as a 64-bit number.

... which has another drawback, besides code complexity: we'd be
exceeding one SHA-256 block with a likely typical key size of 32 bytes.
A maximum of 55 bytes fits in one SHA-256 block (if it's the only one,
so needs padding).  Currently, we have:

16+1+32 = 49

If encoding round+keylen as 64 bits:

16+8+32 = 56

This is one byte too much, resulting in a 2x slowdown.

So maybe we shouldn't encode the full keylen for that reason.  Maybe
encode round+keylen as 32-bit, or use the approach I had suggested (with
round number hashed in last).

Alexander