Using inexpensive off-the-shelf components, an information security expert has built a mobile platform that can clone large numbers of the unique electronic identifiers used in US passport cards and next generation drivers licenses.

The $250 proof-of-concept device - which researcher Chris Paget built in his spare time - operates out of his vehicle and contains everything needed to sniff and then clone RFID, or radio frequency identification, tags. During a recent 20-minute drive in downtown San Francisco, it successfully copied the RFID tags of two passport cards without the knowledge of their owners.

Paget's contraption builds off the work of researchers at RSA and the University of Washington, which last year found weaknesses in US passport cards and so-called EDLs, or enhanced drivers' licenses. So far, about 750,000 people have applied for the passport cards, which are credit card-sized alternatives to passports for travel between the US and Mexico, Canada, the Caribbean, and Bermuda. EDLs are currently offered by Washington and New York states.

"It's one thing to say that something can be done, it's another thing completely to actually do it," Paget said in explaining why he built the device. "It's mainly to defeat the argument that you can't do it in the real world, that there's no real-world attack here, that it's all theoretical."

Use of the cards is expected to rise as US officials continue to encourage their adoption. Civil liberties groups have criticized the cards and a travel industry association has called on the federal government to suspend their use until the risks can be better understood.

The cards make use of the RFID equivalent of optical barcodes known as electronic product code tags, which are widely used to track cattle and merchandise as it's shipped and then stored in warehouses. Because the technology employs no encryption and can be read from distances of more than a mile, the tags are highly susceptible (PDF) to cloning and tracking, researchers have concluded.

Paget's device consists of a Symbol XR400 RFID reader (now manufactured by Motorola), a Motorola AN400 patch antenna mounted to the side of his Volvo XC90, and a Dell 710m that's connected to the RFID reader by ethernet cable. The laptop runs a Windows application Paget developed that continuously prompts the RFID reader to look for tags and logs the serial number each time one is detected. He bought most of the gear via auctions listed on eBay.

And if you read on, we'll show you video proof that the thing actually works.