From: dlv@bwalk.dm.com (Dr.Dimitri Vulis KOTM)
Date: Wed, 24 Jul 1996 01:31:41 +0800
To: cypherpunks@toad.com
Subject: Re: Decrypt Unix Password File
In-Reply-To: <01BB78C7.358738E0@ip73.i-manila.com.ph>
Message-ID: <9HRiRD9w165w@bwalk.dm.com>
MIME-Version: 1.0
Content-Type: text/plain


Jerome Tan <jti@i-manila.com.ph> writes:

> How can I decrypt Unix password file?

If the /etc/passwd file does not use shadow passwords, then the second field
of each line contains the 'salt' and a value dependent on both the salt and
the secret password.

One can try to compute the function of all reasonable dictionary words with
the salts in the /etc/passwd file, and hope that some of them match the
values listed in the file.

There are many programs that do this, e.g., look for 'crack'.

This attack can be made more difficult if you force your users not to use
easy-to-guess passwords, and if you use something like NIS and shadowing to
make the public part of the passwords harder to get.

---

Dr.Dimitri Vulis KOTM
Brighton Beach Boardwalk BBS, Forest Hills, N.Y.: +1-718-261-2013, 14.4Kbps