phc-discussions - Re: [PHC] How important is salting really?

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Date: Sat, 13 Dec 2014 00:09:16 -0800
From: epixoip <epixoip@...dshell.nl>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] How important is salting really?

On 12/12/2014 11:56 PM, Jeremy Spilman wrote:
> On Fri, 12 Dec 2014 23:03:13 -0800, epixoip <epixoip@...dshell.nl> wrote:
>
>> You eliminate more salts faster by looping over the salts for
>> each word in a wordlist, as opposed to looping over the wordlist for
>> each hash.
>
>
> I'm going to try (and likely fail) to channel @scoobz here;
>
> If you are optimizing the attack by iterating through each salt and
> then going on to incrementally less popular passwords, (makes perfect
> sense) then I would imagine if the defender naively does H(pwd||salt)
> you could gain a significant optimization from that. Do you ever see
> this in practice?


Yes, and this is immediately observable.

Hashtype: md5($pass.$salt)
Workload: 1024 loops, 256 accel
Speed.GPU.#1.: 12279.9 MH/s

Hashtype: md5($salt.$pass)
Workload: 1024 loops, 256 accel
Speed.GPU.#1.:  6757.1 MH/s