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Re: passwd hashing algorithm
From: watt () sware com (Charlie Watt)
Date: Wed, 19 Apr 1995 09:41:14 -0400 (EDT)


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X-Sensitivity-Label: 1,CMW+3.0/SCO_2.1/sware.com,UNCLASSIFIED
X-Information-Label: 1,CMW+3.0/SCO_2.1/sware.com,UNCLASSIFIED



1. 25 iterations of DES with the first 8 bytes of the
   password as key, followed by 25 iterations of DES
   with the second 8 bytes of password as key.
   [ ... better version deleted ... ]
(1) can be broken on a workstation with ~ 2^32 steps (and
very little in the way of memory);

I've never seen anything resembling a convincing argument for this point.


Hrmm, well, I could give you the crypto explanation...do you
want me to?  [Keywords: meet-in-the-middle, birthday attack]

....


SecureWare uses a mechanism similar to this and it is part of one of
their security offerings.  I've used a slightly different, but similar,
approach for several years


We do not.  See below.


Good lord!  Can anyone give more details?  [ The details
tend to matter in this business: something similar but
slightly different might be safe. :-) ]

Sorry to the rest of you bugtraq folks: I would be taking
this to personal email, except for the fact that someone
actually uses the broken scheme -- yikes! -- that's my ObBug.


This is most certainly NOT SecureWare's password implementation, although
I can understand why there might be some confusion.  SecureWare has modified
the behavior of password hashing not to increase the strength of the
underlying crypt(), but to increase the size of the possible password space
and the resulting hash value.  The algorithm breaks a password into crypt-
sized blocks, running crypt() across each block.  The salt for each block is
derived from the ciphertext of the previous block to provide linkage between
the individual blocks.  The resulting hash is the concatenation of the 
various ciphertext blocks, prefixed with the initial salt.

This strong mechanism, combined with shadow password files and configurable 
password controls (random pronounceable password generator, password aging, 
minimum allowable lengths, attack detection and account lockout, etc...)
allow a system security officer to be as paranoid as they choose -- e.g.,
passwords can be configured to look like standard Unix, they can be configured
to be 128 byte random passwords, or they can be configured somewhere in
between.  As an example, my password is between 8 and 16 bytes long.  Its
entry in the shadow password database looks like:

watt:u_name=watt:u_id#124:\
        :u_pwd=8F0Ovkj7jA9jE.ofsJ4MaIt6:\

Charles Watt
SecureWare, Inc.

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