From: Andrew Meredith <meredith@ecid.cig.mot.com>
Date: Mon, 3 Feb 1997 12:11:41 -0800 (PST)
To: Greg Rose <cryptography@c2.net
Subject: Re: PCS Encryption?
Message-ID: <199702032011.MAA01060@toad.com>
MIME-Version: 1.0
Content-Type: text/plain


Greg Rose wrote:
>
> The three different digital standards in North America are TDMA,
> CDMA, and GSM (in NY and DC only AFAIK).

GSM is also a Time Division Multiple Access (TDMA) system. In it's 
original form it uses specrum around 900 MHz, which I believe not to be 
available in the US. Shame really, I can roam with my GSM phone over 
pretty much the rest of the planet ... except the US.

Anyway, there are two higher frequency derivatives, PCS1800 & PCS1900, 
which have been deployed in the US. I'm not involved directly in the US 
market so I'm not sure where. I assume however that these are the 
systems to which Greg refers.

> Newer analog phones use at least some of this, but I don't know much
> about them. I'll ignore GSM.
              ^^^^^^^^^^^^^^^
Aww shame ;)

> The conclusion is that neither way of doing it is truly
> cryptographically strong, but both are a lot better than
> listening to Princess Di call Newt "Squidgy" on a Radio Shack
> scanner.

GSM uses the A5 algorithm which *is* cryptographically strong, but is 
unfortunately considered to be top secret stuff. If, however, you were 
to pick up a copy of "Applied Cryptography, 2nd Edition" by Bruce 
Schneier you may find something of interest.

I hope that you'll work out from my .sig why I can't say much more.

Hope this helps

Andy M

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