Tech vs. Tech

As potentially privacy-wrecking technologies proliferate, so do technological means to stymie them. From The Australian:

Personally-controlled blocker tags may offer a technical solution to unwanted consumer tracking by radio-frequency ID chips as retail stores begin to adopt (RFID) for inventory and anti-theft purposes.

RSA Security has unveiled a prototype Blocker Tag that effectively "spams" any scanner that attempts to read RFID tags without the right authorisations.
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But consumer and privacy groups warn that the unique serial number transmitted by each RFID tag could be used to surreptitiously track people or goods. They fear shoppers may unwittingly broadcast information about their purchases and even the brands of clothing they are wearing as they shop.

Scanned data also could be linked to other customer information to create detailed marketing profiles, or to credit card payment records.
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RSA's patent-pending Blocker Tag works by "shielding" chips within close proximity, but the blocker does not interfere with normal RFID.

"Blockers can't be used to circumvent theft-control systems or to mount denial-of-service attacks," Kaliski says. "Instead, they work by creating a hostile environment for scanners that are not authorised to read information from legitimately purchased items."