From: Matthew J Ghio <mg5n+@andrew.cmu.edu>
Date: Sun, 17 Apr 94 11:31:37 PDT
To: cypherpunks@toad.com
Subject: Re: rng, anyone?
In-Reply-To: <9404170405.AA28846@ah.com>
Message-ID: <8hgM0uC00Vpc9g7nQ2@andrew.cmu.edu>
MIME-Version: 1.0
Content-Type: text/plain


hughes@ah.com (Eric Hughes) wrote:

> There is a problem with generating random numbers by repeated
> iterations of a hash function when these numbers will be used to
> simulate an encrypted message body.  The body can be seen to be
> generated by the algorithm.  All you do is to apply MD5 to the first
> block and see if it's equal to the second block.  This completely
> identifies the message as a hash-chain generation, and thus as a fake
> message.
> 
> Indistinguishability is a harder criterion to simulate than other
> notions of randomness.

Try xoring the output with a secret value between MD5 hashes.