phc-discussions - RE: [PHC] Different cost settings and optional input

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Date: Sun, 17 Feb 2013 20:06:07 -0600 (CST)
From: Steve Thomas <steve@...tu.com>
To: discussions@...sword-hashing.net
Subject: RE: [PHC] Different cost settings and optional input


On February 17, 2013 at 6:01 PM Marsh Ray <maray@...rosoft.com> wrote:
> From: Steve Thomas [mailto:steve@...tu.com]
> >
> > Actually we're both wrong. There are 175 million users at the time
> > of the break in. There are 5,787,239 unique hashes that were
> > released
>
> Do we know if the released unique hashes represented all the unique hashes of
> the 175 million?
> 
My guess is that 13 million account hashes got compromised. I'm going off
RockYou's data (2.2 users/unique password). I thought 30.2 users/unique password
looked a little high.


> > (once you remove the first 8 characters of the hash because some
> > hashes had their first 8 characters zeroed out).
>
> Did those turn out to be the easiest to break? There was speculation that
> attackers had zeroed out the beginning of the ones they'd been able to break.
>
I heard that too, but I don't believe that is the case since there are 670,781
duplicates in the list when you remove the first 8 characters.


> > N_50 = 100,000
> > speed = 1 billion/s
> >
> > unsalted: 0.1 ms (100,000 / 10^9)
> > salted: between 4 hrs 52 min and 2 hrs 26 min (175,000,000 * 100,000 / 10^9
> > to 175,000,000 / 2 * 100,000 / 10^9)
>
> So, at least in the absence of a meaningful work factor, we can conclude:
>
> 1. If the attacker is targeting a specific user or small set of user(s), salt
> doesn't help much at all.
>
True, but salt prevents the use of rainbow tables. Which would help a lot in
recovering a few hashes.
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