From: "Perry E. Metzger" <perry@imsi.com>
Date: Tue, 7 Jun 94 05:32:01 PDT
To: gtoal@an-teallach.com (Graham Toal)
Subject: Re: The Crypto Home Shopping Network
In-Reply-To: <199406062335.AAA27342@an-teallach.com>
Message-ID: <9406071231.AA10475@snark.imsi.com>
MIME-Version: 1.0
Content-Type: text/plain



Graham Toal says:
> I think RC4 is the 32 bit cypher used in cellular phones throughout
> Europe.

No.

(RC4 is simply Rivest Cipher 4, or Ron's Cipher 4. Its a stream cipher
that RSA sells. It has nothing to do with the GSM standards.)

> Rumour has it it can be cracked in realtime.

No.

(It is true that only 40 bit key (or smaller) versions of RC4 are
exportable, and that exported RC4 is often pretty quick to crack as a
result. Even under this limited sense of the exported keysize-limited
versions, however, it isn't real time.)

> The actual
> cypher is secret though,

No.

(Its merely trade secret protected -- you get full details if you buy
a license from RSA, which is not an uncommon thing. No security
clearances or anything. If you have a copy of any one of several Lotus
or other programs you have RC4 right on your machine, and if you have
a disassembler you can likely find out exactly how it works.)

> which makes it *very* interesting that
> it'll be available in a software product.

No.

(Its available all over the place. Dozens of products in your local
computer store use it, and all are software.)

Perry