Cooperation of Telecommunications Providers with Law Enforcement

by Philip R. Karn, Jr.

COOPERATION OF TELECOMMUNICATIONS PROVIDERS WITH LAW ENFORCEMENT
Letter to Congress

Senator Dennis DeConcini
United States Senate
Washington, DC 20510

Dear Senator DeConcini:

Yesterday I read a most disturbing computer network article about a piece of legislation you are proposing that apparently attempts to regulate the use of cryptography to protect the secrecy of private communications. I refer to this excerpt:

Senate 266 introduced by Mr. Biden (for himself and Mr. DeConcini) contains the following section:

SEC. 2201. COOPERATION OF TELECOMMUNICATIONS PROVIDERS WITH LAW ENFORCEMENT

It is the sense of Congress that providers of elec- tronic communications services and manufacturers of electronic communications service equipment shall ensure that communications systems permit the govern- ment to obtain the plain text contents of voice, data, and other communications when appropriately authorized by law.

The author of the article continues:

The referenced language requires that manufacturers build trap-doors into all cryptographic equipment and that providers of confidential channels reserve to themselves, their agents, and assigns the ability to read all traffic.

I would like to know if this is indeed the intent of your legislation. If so, it will be the most futile exercise of authority since King Canute set up his throne on the beach, ordered the sea to withdraw and probably got his feet wet for his trouble.

I would like the opportunity to explain.

First of all, this legislation will not serve its ostensible purpose (facilitating a legitimate police investigation involving encrypted communications or stored data). Quite simply, cryptography exists; it cannot be uninvented. And with today's powerful, inexpensive and readily available computer technology, anyone - law-abiding citizen or crimi- nal - can apply a little technical knowledge and build and operate his own cryptographic communications system.

You see, with the right software, even the simplest personal computer becomes an excellent cipher machine - and the software is readily and widely available. I know of perhaps six public-domain programs that do the National Bureau of Standards' Data Encryption Standard (DES); I wrote one of them. DES software is also available in several publicly available books and magazines and from several commercial suppliers. Even without all this software, an interested programmer can find the complete specifications for DES in any of several dozen textbooks on cryptography - not to men- tion the official Federal standards themselves.

And DES is not the only cryptographic algorithm available to the public. Because of concerns about possible weaknesses in the DES (including unproven allegations that the National Security Agency introduced a "trap door" into the design), research into stronger alternatives has been brisk. New algorithms appear all the time, and they come from cryptolo- gists all over the world. The NSA has abandoned its attempts to control the publication of private cryptographic research because it is clearly protected by the First Amendment.

It is precisely because computers are so easily turned into cipher machines that your reference to "providers of elec- tronic communications services" is so pointless. A smart criminal won't trust anyone with his plain text that he doesn't have to - especially not a communications provider subject to subpoena. He'll encrypt on an end-to-end basis with his own computers, his own cryptographic software and with cryptographic keys known only to him (and protected by his Fifth Amendment right against self-incrimination). Com- munications service providers won't have the opportunity to turn plain text over to law enforcement because they'll never see it.

You also refer to "manufacturers of electronic communica- tions service equipment," which I assume means "manufactur- ers of cryptographic hardware." But this would be equally ineffective: no criminal would use a ready-made cipher machine with a "trap door" built into it when he can so easily turn his own personal computer into a cipher machine without a trap door, and at much lower cost. Indeed, spe- cialized cryptographic hardware has only one real advantage over cryptographic software running on general purpose com- puters: the hardware is generally more tamper-resistant. This is usually important only in highly sensitive applica- tions such as banking, where one does not want to trust one's employees too much. It is irrelevant where the owner and user of the computer, the person being protected by cryptography and the person who knows the key are all the same.

This brings me to the second fundamental flaw in your pro- posed legislation. Even if "trap doors" were installed in cryptographic equipment of the type used by banks (among others), how could their use be limited to persons "duly authorized by law"? Experience has shown electronic vandals (popularly known as "hackers" or "phone phreaks") to be highly adept at discovering and exploiting hidden security weaknesses in computer and communication systems. What is to prevent such persons from discovering and exploiting weaknesses deliberately introduced in response to your legislation?

They certainly wouldn't remain secret for long. Every modern cipher is designed to rely entirely on the secrecy of the key for its security. The design of the cipher itself must be assumed to be completely public, because eventually it will be. (This philosophy is captured in a popular computer science saying: "Security through obscurity doesn't work.")

Indeed, what procedures could guarantee that "trap doors" would not be abused by law enforcement or other government personnel not properly authorized by court order? The rise of computer technology has opened up many opportunities for invasion of privacy and the abuse of government power. It is only fitting that the same technology in the hands of indi- viduals can also put some real teeth into the guarantees of the Fourth and Fifth Amendments.

The government is simply going to have to get used to its citizens using cryptography that it cannot break. The police may have to give up on wiretaps and information seizures and resort to the more traditional (and less invasive and less easily abused) ways of conducting investigations, such as informants and grants of immunity for testimony. They may even have to give up entirely on enforcing certain laws, e.g., those prohibiting the mere possession of information. Perhaps the government can then redirect its resources toward enforcing laws that make more sense.

A popular metaphor states that the computer is an extension of the human mind. With cryptography, this metaphor becomes reality in one important way - a user can make the informa- tion stored in a computer or transmitted over a phone line just as private as the information in his own mind. And I wouldn't have it any other way in a free society.

Senator, I urge you to abandon this ill-advised proposal. At best, it will be ignored. At its worst, it would decrease security for law-abiding citizens while doing nothing to help bring clever criminals to justice.

Sincerely yours,

Philip R. Karn, Jr.