From: smb@research.att.com (Steven Bellovin)
Subject: Re: Clipper considered harmful
Distribution: inet
Organization: AT&T Bell Laboratories
Lines: 34

In article <WCS.93Apr21204048@rainier.ATT.COM>, wcs@anchor.ho.att.com (Bill Stewart +1-908-949-0705) writes:
> On the other hand, I can easily see them recording the traffic for
> "interesting" people, such as dissidents, suspected criminals,
> foreign telephone calls, and anybody noticed using encryption.
> As Ken Shiriff speculates, recording encrypted traffic will probably
> be judged not to be an invasion of privacy pretty soon ....

As I read the current wiretap law, it would not be legal now.  On the
other hand, assuming a legislative change, recording but not decrypting
Clipper conversations would probably be found constitutional by the Supreme
Court, using the same reasoning (or the lack thereof...) by which they
permit random roadblocks to check for drunk drivers.

Incidentally, if we use that as our model, the Court will likely not
uphold selective recording.  (On the other hand, I don't think they've
thrown out ``drug courier profiles'' yet.  Must be that exception to
the Fourth Amendment that I can never find in my copy of the Bill of
Rights.)

A lot -- and I mean a *lot* -- will depend on exactly how Clippertaps
(or Tipperclaps, for encrypted music?) are used.  Don Alvarez showed in
the latest RISKS digest that it's possible to prevent the cops from
reading traffic after their warrant expires.

That is -- the cops send the LEF to the F-holder.  The F-holder strips
off F, and sends U[K],N to the escrow agents.  They send either U or K
to the cops.  (Don says U, I say K.)  The cops can't use U in the
future, because they can't strip off F.  The F-holder never sees U.  In
Don's model, the escrow agents can't read the traffic, because they
don't have K; in my model, they have K, but not the message itself.
And I trust that more because I think the cops and the FBI (the
F-holder) are more likely to collaborate on breaking the rules.  The
net result is that by involving the F-holder and the escrow agents on
every tap, we can avoid extending permission to tap.
