Citation: A. Juels and J. Brainard. Soft Blocking: Flexible Blocker Tags on the Cheap. In S. De Capitani di Vimercati and P. Syverson, eds., Workshop on Privacy in the Electronic Society (WPES), pp. 1—7. 2004.
Abstract: As originally proposed, RSA® Blocker Tags are special-purpose RFID tags. In exploring a range of deployment tradeoffs for blockers, scientists at RSA Laboratories have devised an alternative: A way to use essentially ordinary RFID tags to achieve RSA®-Blocker-Tag-like functionality. Such tags are called "soft" blockers.
"Soft" blockers do not always achieve privacy guarantees as
strong as those of normal blocker tags. They do have some advantages,
though. A soft-blocker system is designed to require only the addition
of a writeable bit to ordinary RFID tags. "Soft" blocking also
facilitates a particularly sophisticated range of blocking policies. “Soft”
blocking is a technical basis for the RSA Laboratories RXA Pharmacy demo.