From: "Ian Farquhar" <ianf@wiley.sydney.sgi.com>
Date: Thu, 15 Sep 94 18:25:33 PDT
To: cme@tis.com>
Subject: Re: if this is RC4
In-Reply-To: <9409151906.AA05269@snark.imsi.com>
Message-ID: <9409161122.ZM2097@wiley.sydney.sgi.com>
MIME-Version: 1.0
Content-Type: text/plain


On Sep 15,  3:06pm, Perry E. Metzger wrote:
> > Assuming for the moment that alleged-RC4 came from the keyboard of Ron
> > Rivest,

> Well, from his mind -- its probably a reverse engineering job. It
> looks like it may be interoperable, which would imply that its real...

If it is, then the person who did it has gone to a lot of trouble to make
the source layout and coding style very similar to the publicly available
MD[245] sources.  Compare them and you'll see what I mean.  One of the original
reasons I thought that this was a fake was the similarity (adds credibility),
but when it was verified I began to think that this is, in fact, the real
source
from RSADSI.  I don't think that this is a reverse engineering job, because
I can't see any motive for anyone to put the work into making the code look
so similar.

> Hard to tell. Its remarkably simple -- the simplest cypher I've seen
> in some time. It obvioously needs to be studied in detail. The
> possible excitement comes from its speed...

I think that we must bear in mind that most of us are familiar with block
ciphers, and that there aren't a lot of stream ciphers out there which are
widely used right now.  The only others I know of are the various LFSR's
(which are pretty simple themselves), and that alleged early prototype
A5 (which was itself a group of LSFR's too).

								Ian.