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

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Message-ID: <op.xqqkc8lzyldrnw@laptop-air>
Date: Thu, 11 Dec 2014 19:37:46 -0800
From: "Jeremy Spilman" <jeremy@...link.co>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] How important is salting really?

On Thu, 11 Dec 2014 19:13:34 -0800, Peter Maxwell <peter@...icient.co.uk>  
wrote:

> (C) may come back into play again, albeit marginally.
>
> If commonly chosen passwords have an incidence of, say, 0.5% in a  
> database (not unreasonable from what I can tell), >there is a suitably  
> large number of hashes in the database, and the work involved in  
> calculation of a single hash is high >then it might be of use.

I'm not sure if we can take the Adobe leak as a good example, but in that  
case their single-key ECB mode had a similar effect as an unsalted keyed  
hash, in that we can see duplicates, but can't run a dictionary attack.  
Apparently 1,911,938 out of 130m were '123456', and the Top 100 passwords  
were used by almost 6,000,000 accounts. [1]

Salting at least makes a big difference in the special case where you have  
a keyed hash with an un-leaked key.

[1] - http://stricture-group.com/files/adobe-top100.txt
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