[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Fri, 12 Dec 2014 08:10:27 -0800
From: "Dennis E. Hamilton" <dennis.hamilton@....org>
To: <discussions@...sword-hashing.net>
Subject: RE: [PHC] How important is salting really?
-----Original Message-----
From: epixoip [mailto:epixoip@...dshell.nl]
Sent: Friday, December 12, 2014 03:13
To: discussions@...sword-hashing.net
Subject: Re: [PHC] How important is salting really?
[ ... ] In other words, an algorithm must not rely on solely upon salting. In other
other words, something like sha256(s.p) is insufficient.
<orcnote>
I am having difficulty understanding the case where
H_i = hash(salt_i, pw_i*)
is necessary but not sufficient.
It would help me to understand the use case better.
Assume that everything above but pw_i* is known to
the adversary. The "hash" is a cryptographically
adequate near-one-way transformation and whatever
the work factor and resource costs are, they are
not too costly for the defender.
Now, for a corpus of (salt_i, H_i) pairs, salt_i
Are assured to be unique. Assume salt_i and H_i
are of the same order (number of bits) and the
salt_i are at least half cryptographically-
random bits.
What are the search model and initial conditions
such that cracking one pair for pw_i* makes
cracking a different pair easier to any practical
degree? Put differently, what must N, the size
of the corpus being attacked, be for the N-th
crack to be twice as fast as the first, and how
does that work out as an average cost per crack?
I think this fits the password-hashing conditions,
with regard to the presumption that all but the
pw_i* are disclosed (and any other parameters
are fixed for the given corpus).
</orcnote>
Powered by blists - more mailing lists