Subject: Clipper Chip

From: Tony Harminc <[email-masked]>
Date: Fri, 23 Apr 93 00:29:38 EDT

Thoughts on the Clipper Chip:

1) One of the selling points of the Clipper chip is that US companies will be
able to use it to effect secure communication between their home offices and
branches in foreign countries.  In particular, it is implied that it is the
governments of those foreign countries that will be thwarted in their attempts
to listen in to the corporate secrets of America.

Now why would any "friendly" foreign government (e.g. Canada, France,
New Zealand) imaginably permit Clipper to be used on its territory
unless it too has access to the keys for "law enforcement purposes" ?

So if XYZ Corp. wants to talk in private with its French subsidiary XYZ
France, SA., the French government will want access to the escrow agents so
that it too can present a court order (according to French law, of course) and
be given XYZ's key, if it suspects wrongdoing on the part of XYZ France.  But
this clearly won't do.  The US escrow agents will presumably be subject to US
law and might be able to refuse a French court order on some US constitutional
grounds.  So the French will have to have their own pair of agents, and -
since there is no advance control of which chips will end up in France - these
French agents will have to have the complete list of all keys.  Now multiply
this by a dozen or so friendly countries, with an equal number of different
legal systems and constitutions...

2) Presumably the reason for keeping the algorithms secret is to prevent
competitive manufacture of chips (or software) that can communicate with
Clippers from being produced.  (Such competitors might somehow forget to send
their key lists to the escrow agents.)

I know almost nothing of the technology, but it seems far fetched to me that a
chip can be manufactured that *absolutely, positively* cannot be reverse
engineered, or at least satisfies something analogous to being computationally
infeasible to reverse engineer.

There was no mention of quantum effects, but I know of no other way to even
begin to make something that can't be examined with appropriate probes.  I
hope some hardware experts will say something on this topic.  Or is it that
the hardware design can be reverse engineered, but the algorithms themselves
are one-way encrypted ?

3) It is not clear to me how tapping of bidirectional communications
works.  If the police have a court order to tap the phone of suspected
criminal X, and they find that he is holding a Clipper-encrypted
conversation with previously unknown person Y, will they be able to
decrypt only what X says if they have only X's key from escrow ?
Or will they automatically apply for Y's key too, on the grounds
that he is an associate of X ?

Ordinary analogue phones (and networks) echo a small amount of the received
signal to the sender, but an encrypting phone will have digitized and
encrypted the signal before it gets echoed (even if there is a modem and
analogue circuit in the loop).

Tony Harminc, Apios Systems Toronto,  [email-masked]