"A lot of this is done not only without the consumer's knowledge - it's beyond the grasp of most consumers how it works. Nontechnical people don't know what the risks are. They just want to buy things and have their privacy and credit card numbers protected," said Avi Rubin, a Johns Hopkins University computer science professor who worked with Massachusetts researchers to crack the encryption scheme of the ExxonMobil Speedpass in 2005.
Although he and many other computer security specialists say they don't believe the tags pose a serious threat today, they are concerned about the future.
"You can look at this at two different levels: whether it's worthwhile for you as an individual to fuss with wrapping your cards in some sort of sleeve, or looking at the systemic issue: how we got to a point where these cards do make this information available remotely," said Edward W. Felton, a professor of computer science and public affairs at Princeton University, whose graduate students became famous for penetrating the security of electronic voting machines.
RFID chips are encoded with digital information - which could be the inventory number for a pair of jeans, or a credit card number, an employee ID, or driver's license data, medical records or passport information.
When an RFID reader sends out an electromagnetic query, the RFID chip transmits the information. While the industry is selling RFID applications as diverse as radio dog-collars and fitness monitors, the technology has also spawned a tiny counter-industry of firms that produce metal-lined wallets, passport sleeves and other devices to shield RFID-enabled documents and credit cards.
Activist Web sites hawk anti-RFID T-shirts and other paraphernalia.
Even vocal RFID critics say the problem hasn't reached a crisis level - which makes it hard to argue their case.
Lee Tien, senior staff attorney for the San Francisco-based Electronic Frontier Foundation, said those who raise the alarm realize how it would have felt to warn the public about air pollution the day the Model T was introduced.
The EFF has opposed use of the technology on several fronts. And as a parent, Tien spoke against a proposal for an enhanced California driver's license that could broadcast the name, address, height and weight of drivers - such as his 16-year-old daughter.
But he doesn't oppose the technology itself. "I would honestly have no problem using RFID devices if I knew I could control who was going to read them," Tien said.
