Excerpts from the Clipper announcement, with some questions:



In these two sections the phrases `or other legal order' and `normally a
court order' imply there is some other way or ways of doing a legal
wiretap. What is/are these? How do they affect the way people who trust the
system of court orders to protect them feel about this escrow system?

The second section shows the sequence of events.
The law enforcer, armed with his warrant, attaches his headphones to the
line with his croc-clips (remember, these are the folk who couldn't cope
with digital telephony) and hears a load of modem-like tones (we are
talking analogue telephony here).
What next? What modulation scheme do these Clipper boxes use?
Is it possible to record the tones for use after the keys are obtained?
I thought it was quite difficult to record a modem session at some
intermediate point on the line. Maybe they have taken a crash course
in data comms and have a unit that demodulates the tones and stores the
digital stream for decryption later. This would still suffer from the
same problems as trying to record the tones as the demodulator would not
be at one end of the line. If calls can't be recorded for decryption later
it would be quite easy to foil the system by buying lots of Clipper units
(these are supposed to be cheap mass market items) and using them in turn.

How tolerant is the modulation scheme to errors? These things are proposed
for use by US corporations to secure their foreign offices, where phone
line quality may well be poor. It seems hard enough to me to get digitised
speech of any quality into something a modem can handle without having to
add lots of error correction to keep the decryption in sync.


This raises an intersting question in the UK. Here it is illegal to connect
anything to a public telecomms network without it being approved by a body
called BABT. It has been stated, either here or in the uk.telecom group,
that they will not approve equipment that does encryption. I don't know
if this is true or not, but this would make a good test case.
Perhaps `friendly' countries, and the UK may still qualify, will get
to fish in the escrowed key pool as well.
