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

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Message-ID: <CAMtf1HtD8b+WBSJO-zO96jK8xweQbaeo1buOFV_68VX+e=gPow@mail.gmail.com>
Date: Fri, 12 Dec 2014 18:39:57 +0800
From: Ben Harris <ben@...rr.is>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] How important is salting really?

On 12 December 2014 at 17:53, epixoip <epixoip@...dshell.nl> wrote:

> Thus the salt table shrinks with each successful
> crack, and the effective speed of the attack increases with each
> eliminated salt.
>
>
A rather confusing way to describe things. If we are attacking all password
hashes, one password at a time (from the most common down). Then each time
we find a match, the pool of hashes decreases and subsequent passwords can
be search faster.

At the moment an attacker can calculate somewhere between 10^10 - 10^15
SHA256 per dollar in electricity. They can scan a list of 1 million common
passwords for about a thousandth of a cent. If this cost were much higher
(>> $1), then the economics of the attacks would change.

If there was no salt, then the cost would be drastically lower and the
attacker could start the attack before getting the hashed passwords.

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