Subject: File 6--Clipper Questions and Answers in a Nutshell

From: Mark Lloyd <[email-masked]>
Date: 18 Feb 94 15:23:33 EST

Clipper Q and A
By W. Mark Lloyd

WHAT IS THE CLIPPER CHIP?

The Clipper chip is an encryption chip using an algorithm called
Skipjack.  The Skipjack algorithm was developed by the National
Security Agency (NSA) for the National Institute of  Standards and
Technology (NIST).  Data encrypted using the Skipjack algorithm can be
decrypted using a secret process that requires two separate keys.
These keys would be escrowed separately by NIST and the Department of
Treasury.  Under the plan, a law enforcement agency  would require a
court order to get the two keys that would have to be combined to
decrypt a transmission generated with  a Clipper chip.

HOW DOES THE SKIPJACK ALGORITHM DO THIS?

Encryption algorithms use numbers called keys that are like
combinations to a lock.  Messages are encrypted and decrypted much the
same as locks are locked and unlocked.  The key to any Clipper encoded
message is itself encrypted using a key derived from two other keys
that are stored separately.  The encrypted  key and a number that
identifies the chip that sent the message are then encrypted with
another key that is common to many other chips.  All of this is sent
along with the encrypted original message. This is done so if a law
enforcement  agency wants to decrypt a message the process can be
reversed: The outer portion of the encrypted key is decrypted to get
the number that identifies the unit  that sent the message. This is
used to obtain the two separate escrowed keys  that are then combined
to decrypt the session key  that allows the original message to be
decrypted.

	Lets look at another way. You have the session key S, the key E
derived from the two escrowed keys,  the family key F, the message M
and the chip identification number C.  Its all  put together  like
this:  (M encrypted with key S)+(((S encrypted with key E) C
)encrypted with F)

IS THE SYSTEM SECURE?

If everything goes right, according to the a panel of five
cryptography experts who have reviewed it.

WHAT ALGORITHM DOES THE ACTUAL ENCRYPTION?

That is classified information.

BUT AREN'T GOOD ENCRYPTION ALGORITHMS SECURE, EVEN WHEN EVERYONE KNOWS
WHAT THEY ARE, LIKE DES?

Yes.

THEN WHY NOT JUST PUBLISH THE ALGORITHM?

The reasons cited are that compromising the algorithm would be
detrimental to national security.  This means that secret techniques
are used in the algorithm.

SO A GOVERNMENT SECRET IS GOING TO BE IN THOUSANDS OF THESE CLIPPER
CHIPS SHIPPED ALL OVER THE WORLD?

That's the plan.

SO IF SOMEONE FIGURES OUT HOW TO GET THE ALGORITHM FROM THE CLIPPER
CHIPS, OUR NATIONAL SECURITY COULD BE COMPROMISED?

If you follow the NSA's logic, yes.

Law enforcement officials are going to be using the algorithm and the
family key many time to get unit identification numbers.  Lets say
that the algorithm is leaked.  Or one of the black boxes that will be
used to decrypt the chips is compromised and the algorithm and family
keys are generally known?  What will happens then?

The algorithm could be subject to tampering. From our explanation in
question two we would go from this:  (M encrypted with key S)+(((S
encrypted with key E) C )encrypted with F)  to this  (M encrypted with
key S)+(S encrypted with key E) C.  This would leave the chip number
open to tampering.  Also in  theory it would allow a steady attack on
the key E, that would compromise the unit.  This attack is
theoretically better than attacking a message without the law
enforment field, but even if the key S is known (by getting someone
with a chip with to send you a message with a key you have negotiated)
it would still be difficult with todays computer power.   In any case
anyone with anything to hide wouldnt use a Clipper chip for
transmissions they wanted to keep secret from law enforcement
authorities.

MOST ENCRYPTION IS DONE WITH SOFTWARE.  CAN THE SKIPJACK ALGORITHM BE
USED IN SOFTWARE ENCRYPTING SYSTEMS?

No.  The nature of the Skipjack algorithm  makes it only useful if it
is  released in a special tamper proof chip.

SO THE ALGORITHM IS ONLY USEFUL FOR APPLICATIONS THAT CAN USE HARDWARE
ENCRYPTION?

Yes.

WHAT IF I WANT TO ENCRYPT A MESSAGE WITH A REALLY SECURE ALGORITHM
BEFORE IT IS ENCRYPTED BY A CLIPPER CHIP?

That would be a simple and obvious way to get around the Clipper chip.

BUT ISN'T MOST ENCRYPTION CURRENTLY DONE USING SOFTWARE ON GENERAL
PURPOSE MICROPROCESSORS?

Yes.

IS CLIPPER GOING TO BE EASIER TO EXPORT THAN DES?

According to the Clinton administration, yes.

IS THERE A FOREIGN MARKET FOR CLIPPER ENCRYPTION DEVICES?

For there to be a market there needs to be a reason for foreign
purchasers to prefer Skipjack or Clipper technology to currently
available algorithms.  This has not been shown to be true.  There a
report in the British press that the NSA has a representative in
London that is  lobbying European governments to adopt the  Clipper
chip.

WHAT IF A FOREIGN GOVERNMENT WANTS TO SPY ON THEIR OWN CITIZENS, WILL
WE GIVE THEM THE KEYS TO DO THIS?

Good question.

What if a foreign government allows the importation of Clipper chips,
but only if they get the keys first?  Would we be responsible for
their abuse?

That question has not been answered yet.

If we only give them the key when they ask, what if we suspect the
keys they want are to spy on a political adversay. What if a foreign
government decides to make an issue of us not giving  them the keys to
a Clipper chip we sold them? How will we deal with this?

We would be in a no win situation.

WILL THE NSA GET THE KEYS TO SKIPJACK UNITS THAT ARE EXPORTED?

Government officials have said to some people that the NSA will not
get these keys. NSA has not yet said this on the record.

HAVE ORGANIZATIONS THAT REPRESENT THE COMPUTER HARDWARE AND SOFTWARE
INDUSTRIES ASKED FOR A NEW ALGORITHM TO EXPORT?

No.  Both the Software Publishing Association and the American
Electronics Association, along with other industry groups, have asked
that the DES algorithm be made available for easy export.  The DES
algorithm is already available all over the world.  DES is classified
as a munition by the US government and cannot be exported easily.

THE ANNOUNCEMENT FROM THE WHITE HOUSE ON FEBRUARY 4 SPOKE ABOUT THE
PROBLEM OF "TERRORISTS, DRUG DEALERS, AND OTHER CRIMINALS" USING
ENCRYPTION.  WILL THE CLIPPER CHIP DO ANYTHING TO PREVENT THESE PEOPLE
FROM USING NON-ESCROWED ENCRYPTION TECHNIQUES?

No. These prople will be able to encrypt with whatever algorithm they
want.

ARE THERE OTHER WAYS OF ESCROWING KEYS VOLUNTARILY, FOR GOVERNMENTAL
AND BANKING NEEDS THAT REQUIRE BOTH CONFIDENTIALITY AND
ACCOUNTABILITY?

Yes.  There is work being done now on techniques that allow much more
flexible ways of voluntarily escrowing keys.