phc-discussions - Re: [PHC] Are password trailing 0's a problem?

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Message-ID: <20140309041430.GA2368@openwall.com>
Date: Sun, 9 Mar 2014 08:14:30 +0400
From: Solar Designer <solar@...nwall.com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] Are password trailing 0's a problem?

On Sat, Mar 08, 2014 at 10:59:58PM -0500, Bill Cox wrote:
> However, while this flaw is certainly not a critical weakness, and
> obviously Escript in compatibility mode needs to continue using PBKDF2
> as-is, for non-compatible mode, or entirely new password hashing
> systems, should we live with such flaws or try to eliminate them?

We should try to eliminate them.

Regarding your idea re: all PHC submissions doing it in the same way,
I'm not so sure.  In each case, the choice might be affected by other
crypto primitives and constructions that a given PHC submission would
use anyway, so that its total complexity is less.  For escrypt, this is
a reason for its non-compat modes to reuse PBKDF2 anyway, just working
around its shortcomings.

Alexander