To be sure, the RFID tags contain no personally identifiable information, but rather what amounts to a record pointer to a secure Department of Homeland Security database. But because the pointer is a unique number, the American Civil Liberties Union (ACLU) and other civil libertarians warn the cards are still susceptible to abuse, especially if their RFID tags can be read and captured in large numbers. Cloning the unique electronic identifier is the first step in creating fraudulent passport cards, they say.

The cards also amount to electronic license plates that could be used to conduct clandestine surveillance. Law enforcement officials could scan them at political rallies and then store them in databases. The tags could also be correlated to other signals, such as electronic tollbooth payment systems or RFID-based credit cards, to track the detailed movements of their holders.

Not that the Feds care

Officials with the U.S. Customs and Border Protection Department say they have no plans to overhaul the technology used in passport cards. RFID signals allow border agents to process travelers more quickly and bring an added level of security to the process, spokeswoman Kelly Ivahnenko said. The cards come with protective sleeves that prevent the RFID tags from being readable, she added, and even if they are captured, she said there is little anyone can do with the information.

"From our standpoint the privacy issues have been misrepresented and blown out of proportion," she told The Reg. "Anytime that you have a new technology and use it in a new way, there are always going to be far-out ways to use information nefariously. We want travelers to be aware of the technology and to know how it works so that they can be comfortable using it."

A spokesman from the US State Department — which processes applications for passport cards and then issues them — declined to comment.

But critics contend the risks are real, especially if RFID-enable identification becomes universal.

"Just like a social security number, the unique identifier number on this document must be properly safeguarded," said Nicole Ozer, technology and civil liberties policy director of the ACLU of Northern California. "If it falls into the wrong hands, it can be used for tracking, stalking, identity theft, and counterfeiting. If the government continues to stick its head in the sand and ignore the very real privacy and security threats that researchers, civil liberties organizations, and even industry groups have repeatedly brought to its attention, the American people will pay a very high price."

If you have tips or insights on this topic, please contact SecurityFocus.