RFID Privacy Using Spatially Distributed Shared Secrets 

Marc Langheinrich, Remo Marti ETH Zurich and Ergon Informatik AG 

Abstract 

Many of today's proposed RFID privacy schemes rely on the encryption of tag 
IDs with user-chosen keys. However, password management quickly becomes a 
bottleneck in such proposals, rendering them infeasible in situations where 
tagged items are repeatedly exchanged in informal situations, in particular 
outside industrial supply-chains or supermarket checkout lanes. An alternative 
to explicit access control management are RFID privacy systems that provides 
access to tag IDs over time, i.e., only after prolonged and detailed reading 
of an item. Such themes can minimize the risk of unwanted exposure through 
accidental read-outs, or offer protection during brief encounters with 
strangers. This paper describes a spatially distributed ID-disclosure scheme 
that uses a (potentially large) set of miniature RFID tags to distribute the 
true ID of an item across the entire product surface. We introduce the 
underlying mechanism of our spatially distributed RFID privacy system and 
report on initial performance results.