From: Jay Prime Positive <jpp@markv.com>
Date: Thu, 4 Feb 93 14:09:22 PST
To: cypherpunks@toad.com
Subject: `Sunday Times' article on GSM changes
In-Reply-To: <9302042024.AA09970@maggie.shearson.com>
Message-ID: <9302041407.aa14565@hermix.markv.com>
MIME-Version: 1.0
Content-Type: text/plain


Speculation: The "A5 `scrambling code'" is used as the spreading code
for a spread spectrum radio.

Spread spectrum radio has some features cypherpunks may find
interesting: both stegnagraphic and cryptographic.  A Spread Spectrum
signal is usualy based on xoring a very high rate "pseudorandom"
bitstream with the intelligence to be transmitted.  The resulting wide
spectrum signal is usualy transmitted via radio.  As a result the
signal is very hard to notice since the watts/hz can be orders of
magnitude under normal narrow band signals (stegnography).  As a
second result, once detected the signal cannot be understood without
syncronizing an identicle "pseudorandom" bitstream at the reciever
(cryptography).  The reason that gov't types would fear the dispersal
of the technology is obvious.  Btw. many of the wireless lans use
exactly this technology.

j'