Ultrawideband Upset

WiMedia, the next generation of wireless connectivity, is raising some interesting questions about privacy. WiMedia, which underlies consumer technologies such as Certified Wireless USB and the planned next iteration of Bluetooth, is based on the concept of ultrawideband radio. It uses short-range, very-low-power signals transmitted across a vast expanse of the radio spectrum—from 3.1 gigahertz to 10.6 GHz. Traditional radio, on the other hand, uses a much higher-power signal across a narrow band of spectrum.

In the United States, the authority to regulate use of the radio spectrum falls to the Federal Communications Commission (FCC). U.S. courts have consistently ruled that the federal government has the power to regulate the airwaves, because radio is interstate commerce. But can the FCC really claim jurisdiction over the minuscule power levels used by WiMedia radios?

The answer to that question is important because the FCC restricts what radio broadcasters, whether licensed (as in the case of radio or TV stations) or unlicensed (as in the case of the millions of people who own Wi-Fi base stations), can do. On many licensed radio services, encryption is not allowed, as a condition of licensing. Amateur radio operators, for example, have never been allowed to send encrypted traffic; they would lose their licenses if they did.

In contrast, concerned that users be able to trust their new wireless systems, the coalition of electronics companies behind WiMedia—the WiMedia Alliance—demands that all ultrawideband radio systems sold under the WiMedia banner be capable of strong hardware encryption and that for some applications, using this encryption capability be mandatory.

So far, FCC regulations that deal with ultrawideband technologies have made no mention one way or the other of the use of encryption. But could the federal government use the authority of the FCC to enforce a law requiring that all ultrawideband transmissions be in the clear? It’s not such a preposterous idea: the government’s hostility to encryption was demonstrated in the 1990s, when it tried to restrict the use of Internet-based encryption technologies. In the end, the borderless nature of the Internet caused the government to admit defeat. There is no such obstacle to controlling low-power radio, however.

In the 20th century, radio meant broadcast, and there was no general expectation of privacy. Anyone in your area could at least pick up your signal. But in the 21st century, the radios we are building right into computer chips emit radio waves at very low power levels, so the expectation of privacy has emerged.

Remember, the laws of physics determine the distance that radio waves can travel. In order to double the distance, we must square the power of the transmission. If we need to send radio waves only a few feet, this law of nature works in our favor. We can build useful short-range radios that require very little power. As it happens, these radios can have very high data rates, high enough, in fact, to replace the cables going into and out of computers, stereos, DVD players, and digital televisions—even high-definition TVs. A living room or an office cubicle can be covered with less than a millionth of a watt per megahertz.

Consumers have clearly expressed the expectation of and desire for privacy in their personal affairs. People do not want their address books, pictures, and files exposed to anyone who comes within a few feet of their laptops, cellphones, or PDAs.

The expectation of privacy in the United States is grounded, in part, by the Fourth Amendment to the Constitution:

”The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.”

Other countries have similar laws. WiMedia is the first radio technology to run at such a low power level that it unambiguously falls under the Fourth Amendment’s reference to ”persons, houses, papers, and effects.” Claiming that all radio communications are interstate commerce or that there can be no expectation of privacy over the public airways seems ludicrous when applied to submicrowatt transmissions across a few meters.

Previously, many legal issues surrounding radio broadcasting were determined within the context of the First Amendment, which guarantees freedom of speech and freedom of the press. But the FCC is chartered to follow the Constitution, and this means enforcing all our rights—Fourth as well as First Amendment rights.

Our right to privacy needs to be protected—and not just legally. Privacy must be built into the technology itself. Strong encryption of private radio signals is a human right, and we as engineers have an obligation to facilitate this.