Renewing your passport soon? You may want to craft a tinfoil sleeve to store it in. That´s because the next generation of U.S. passports, set to hit travelers´ hands by September, will come with a radio transponder and a 64-kilobyte computer chip embedded in their back covers. The chip will store the same information that´s printed in your passport, and the transponder will broadcast it to a reader synced up to an inspector´s computer. IT´s part of a cover-to-cover passport overhaul to make the document harder to counterfeit.

Why the tinfoil? The transponders, also known as radio-frequency identification (RFID) tags, can theoretically send their contents to readers as far as 15 feet away unless they´re shielded by metal. Privacy advocates worry that thieves could use their own readers to secretly swipe your data. But Frank Moss, deputy assistant secretary of state for passport services, says the new passport´s cover will act as a shield, protecting the chip when the book is closed. Even when it´s open, Moss says, the chips will have a broadcast range of only about 10 centimeters and the data will be guarded by an encrypted digital signature.

The U.S. State Department has spent an estimated $15 million developing the new chips, which are seen as the first step to biometric inspections. Initially, an officer will simply compare your face with the digital mug stored on the chip, but the government hopes to implement an on-the-spot face-recognition scan as early as 2007. â€Eventually we´d like to compare the traveler´s image with a watch list,†Moss says. â€We also have room on the chip to introduce iris or fingerprint scanning.â€

Tinfoil case sold separately.