From: Asgaard <asgaard@Cor.sos.sll.se>
Date: Thu, 16 Jan 1997 01:03:08 -0800 (PST)
To: cypherpunks@toad.com
Subject: Re: Newt's phone calls
In-Reply-To: <199701121640.QAA00188@server.test.net>
Message-ID: <Pine.HPP.3.91.970116094730.28526B-100000@cor.sos.sll.se>
MIME-Version: 1.0
Content-Type: text/plain


On Sun, 12 Jan 1997, Adam Back wrote:

>GSM includes A5 encryption here, so basically the whole design is worked out
>- all you'd have to do is rip out the A5 chip and replace with a decent
>encryption system.  Anyone know how modular the design is, for instance if
>it would be possible to give a GSM A5 based cell phone a crypto upgrade
>using published electrical interface standards?  (I want one of those -
>Nokia phone with IDEA + 2048 bit RSA signatures + DH forward secrecy!)

I don't understand what you are getting at here.
This would demand cooperation from the cell phone provider,
with a compatible device at the other end of the airwaves.
Then the call would go unencrypted through much of the
system until it reached the callee's current cell sender
anyway. GSM is alledgedly A5 encrypted only in the air.

And if A5 is a 'decent' algorithm or not is up to discussion.
It hasn't been up on the list for a long time now but from
earlier discussions I remember that the latest versions of
A5, if not 'strong' in a crypto anarchy sense, are susceptible
to attack only from very sophisticated adversaries and certainly
not from Newt's 'couple'.

Asgaard