Clipper trapdoor?

Clipper trapdoor?

Peter Wayner <pcw@access.digex.net> writes:

>My general impression is that the system is secure. Many people
>have played paranoid and expressed concerns that the classified
>algorithm might be hiding a trapdoor. It became clear to me that
>these concerns were really silly. There is a built-in trapdoor
>to be used by the government when it is "legal authorized" to
>intercept messages. The NSA has rarely had trouble in the past
>exercising either its explicitly granted legal authority  or
>its implied authority. The phrase "national security" is a
>powerful pass phrase around Washington and there is no reason
>for me to believe that the NSA wouldn't get all of the access
>to the escrow database that it needs to do its job. Building in
>a backdoor would only leave a weakness for an opponent to exploit
>and that is something that is almost as sacrilidgeous at the NSA
>as just putting the classified secrets in a Fed Ex package to 
>Saddam Hussein.

This raises an interesting question and I draw a totally different
conclusion.  If, as we have been told, the only way for an agency to
obtain the escrow keys is to present a court order, than NSA needs
to obtain such an order to decrypt *any* communication it intercepts.

I don't really understand what Peter means when he says that "NSA has 
rarely had trouble in the past exercising either its explicitly granted 
legal authority  or its implied authority. The phrase 'national security'
is a powerful pass phrase around Washington and there is no reason
for me to believe that the NSA wouldn't get all of the access
to the escrow database that it needs to do its job."

Does this mean NSA would, in fact, obtain a warrant in order to "get all 
of the access to the escrow database that it needs to do its job"?  If so,
this would represent an unprecedented change in the way NSA does "its
job."  NSA has no domestic law enforcement authority, so it would
obviously never be in a position to obtain a law enforcement wiretap
warrant under Title III.  The only possible way for NSA to obtain a warrant
would be under the Foreign Intelligence Surveillance Act (FISA).  But the
Foreign Intelligence Surveillance Court, which issues warrants under FISA,
has ruled that FISA's provisions

   limit the authority to conduct electronic surveillances to the U.S.
   in a geographic sense as defined in sec. 101(i).  The drafters left
   to another day the matter of "broadening this legislation to apply
   overseas ... because the problems and circumstances of overseas
   surveillance demand separate treatment."

In the Matter of the Application of the United States for an Order
Authorizing
the Physical Search of Nonresidential Premises and Personal Property (1981),
footnote 1 (citations omitted).

Consider the following hypothetical: Iraqi agents smuggle Clipper phones
out of the U.S.  Saddam Hussein uses them to communicate with his military
commander in Basra.  NSA intercepts the communications.  Question:  How
does NSA decrypt the messages?

Note that neither Title III (law enforcement) nor FISA (U.S.-based) apply
to this situation, so we have to assume that NSA will not have a court order
to obtain the escrow keys.  I have to conclude that NSA would not be putting
this technology out into the world *unless* it did, in fact, have some way
to
decrypt messages *without* access to the escrow keys.

Am I missing something?


David Sobel
CPSR Legal Counsel

You didn't read the original clipper announcement carefully.  It never
said that all access to the escrowed keys was to be handled through
warrants.  Clearly the other weasel word access techniques envisioned
included requests from the Agencies.

My paranoid fantasy, actually, is that we are really seeing phase I of a
longer term plan, which will result in outlawing non-escrowed keys.  The
way it works is this:

Skipjack is distributed.  A clever group of nameless individuals obtains
some components.  Through significant effort, they determine the
algorithm and family key, and they are published.  Phase II: mock
Agency uproar ensues, NSA claims it tried to be "reasonable" about
escrowed keys, but obviously the bad guys have demonstrated that they
can't be trusted.  The only way to solve the "problem" is to outlaw
non-escrowed key cryptography.

>> Note that neither Title III (law enforcement) nor FISA (U.S.-based)
>> apply to this situation, so we have to assume that NSA will not have a
>> court order to obtain the escrow keys.  I have to conclude that NSA
>> would not be putting this technology out into the world *unless* it
>> did, in fact, have some way to decrypt messages *without* access to
>> the escrow keys.
>> 
>> Am I missing something?

Yes.  Quoting the original Presidential release:

>> Access to these keys will be limited to government officials with
>> legal authorization to conduct a wiretap.

"legal authorization to conduct a wiretap" != "court order".  I've
seen lots of people slip into that habit.  Today, it requires a court
order to wiretap domestic conversations between US citizens.
Presumably, the same conditions apply to Skipjack.  However, that
could change.

As for the example of snooping on Hussein and his officers, you know
exactly how much legal authorization the NSA needs to conduct that
wiretap.  Exactly none.  Hence, it needs no paperwork to get the key
to Hussein's phone.

How the escrow agents make the NSA prove that the keyid in question
belongs to Hussen's phone is an exercise left to the legislature :-/

		Marc