Making RFID more secure

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14 November 2007 News

Information from Frost & Sullivan Technical Insights

In recent years, radio frequency identification (RFID) tags have been finding favour among manufacturers and retailers as a type of next-generation bar-coding system. When queried with a low-power radio signal, a tag - which can exist as either an active or passive device - replies with a brief transmission suitable for challenge/response identification.

The tiny devices are inexpensive, and can be implanted in an object and then read at a distance without contact. While many applications of RFID are relatively low risk, such as providing inventory tracking in warehouse environments, other applications, such as contactless payment systems and personal identification cards and passport control, require a higher level of security.

In this light, Frost & Sullivan has taken note of a proposal from a team of researchers for a novel way to provide a 'fingerprint' for a given RFID tag and to simply generate true random numbers on such a device for cryptographic purposes.

"We believe we are the first to show how a common existing circuit can both identify specific tags and protect their data," said Wayne Burleson, one of the authors of the report. "Our measurements show that initialisation of SRAM produces a physical fingerprint. The frequent powering up of passive tags is continually generating fingerprints."

The fingerprint arises from minute variations in the way dopants are distributed within any static random access memory (SRAM) cell. The differences in dopant distribution lead to differences in threshold voltage that can be used as a fingerprint, the researchers found. Physically random noise produced during device operation can be used as a random number source.

"The low cost of RFID circuits constrains their functionality," Burleson said, explaining that it is difficult to incorporate complicated cryptographic circuitry into a device that is designed to be implanted into the packaging of ordinary household products. Making use of the new technique, which the team calls FERNS (fingerprint extraction and random numbers in SRAM) allows developers to gain functionality without needing to make the device itself more complicated.

For more information contact Patrick Cairns, Frost & Sullivan, +27 (0)21 680 3274, [email protected]

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