From: Tatu Ylonen <ylo@cs.hut.fi>
Date: Mon, 18 Dec 1995 14:35:04 +0800
To: Jyri Kaljundi <jk@digit.ee>
Subject: Re: Motorola Secure Phone
In-Reply-To: <199512152338.XAA22526@pop01.ny.us.ibm.net>
Message-ID: <199512171141.NAA02997@trance.olari.clinet.fi>
MIME-Version: 1.0
Content-Type: text/plain


> What about cellular phones, especially GSM? As I have heard GSM is 
> supposed to be secure, at least thats what the salespersons tell every 
> time they are selling a GSM.
> 
> I know ciphering algorithms A3, A8 and A5 are used in GSM phones, but I 
> know nothing more about them.

I got the following from mjos@math.jyu.fi a couple of months ago.
Unfortunately I was unable to attend or listen on mbone.  Does anyone
know more about this?

>                  University of Cambridge Computer Laboratory
>
>                                SEMINAR SERIES
>
>
> 10th October    Bill Chambers, King's College, London
>                PROBLEMS OF STREAM CIPHER GENERATORS WITH MUTUAL CLOCK
>		CONTROL
>
> ..

> GSM:n salausalgoritmi on juuri tuota tyyppi. Chambers yritti pit tuota
> nimenomaista esitelm jo yli vuosi sitten, mutta silloin viralliset tahot
> puuttuivat asiaan ja esitys peruttiin. Hn on lytnyt algoritmista aukkoja,
> joiden avulla purkuaika saadaan erittin lyhyeksi.
> 
> ps. ne meist, jotka psevt mboneen ksiksi, voivat seurata tapahtumia
>     liven  :)

[Free translation: The GSM encryption algorithm is of exactly that
type.  Chambers tried to have this particular presentation over an
year ago, but at that time the official side interfered and the
presentation was cancelled.  He has found holes in the algorithm that
can be used to make decryption (without key) very quick.

PS.  Those of us who can get access to mbone, can follow it live.]

    Tatu