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Date: Sun, 7 Oct 2012 02:50:34 +0400
From: Solar Designer <solar@...nwall.com>
To: oss-security@...ts.openwall.com
Subject: password hashing
Hi,
I was too shy to spam oss-security with this, but a list member (who is
also on Openwall's announce list) asked me to. Armed with this excuse,
let me tell you that I made two presentations on password hashing this
year. It's everything you wanted to know about password hashing since
1960s to present day and the near future, and more. ;-)
Password security: past, present, future
(with strong bias towards password hashing)
http://www.openwall.com/presentations/PHDays2012-Password-Security/
Password hashing at scale
(for Internet companies with millions of users)
http://www.openwall.com/presentations/YaC2012-Password-Hashing-At-Scale/
Discussion of the latter at /r/crypto:
http://www.reddit.com/r/crypto/comments/10zjdo/password_hashing_for_orgs_with_millions_of_users/
and on john-users (click "thread-next"):
http://www.openwall.com/lists/john-users/2012/10/05/3
(I intend to reply to the questions raised further in that thread.)
SHA-3 is deliberately not mentioned on the slides yet. I briefly
thought of retroactively adding a few mentions of it (YaC 2012 was a day
too early), but decided not to. SHA-3 should be similar to DES (read:
very good) in context of possible defensive use of FPGAs. As to
PBKDF2-HMAC-SHA-3, things are less clear, although it's probably weaker
than PBKDF2-HMAC-SHA-512 (is it also weaker than -SHA-256? than -SHA-1?
not sure). (In this context, "weaker" means it allows for even more
efficient attack-optimized implementations than the other hash type,
resulting in higher passwords tested per second rate for the same
processing cost of defensive use.) I prefer to keep only fairly
reliable information on the slides, and not speculate on important
issues there (but I do speculate here, as you can see). Those of you
who follow @solardiz on Twitter probably already know a bit more on my
expectations and reasoning for throughput-optimized parallelized
implementations of SHA-3, due to the too-many-tweet conversation I had
with @marshray. ;-)
Alexander
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