Noisy tags: A pretty good key exchange protocol for RFID tags

Abstract

We propose a protocol that can be used between an RFID tag and a reader to exchange a secret without performing any expensive computation. Similarly to the famous blocker tag suggested by Juels, Rivest, and Szydlo, our scheme makes use of special tags that we call noisy tags. Noisy tags are owned by the reader's manager and set out within the reader's field. They are regular RFID tags that generate noise on the public channel between the reader and the queried tag, such that an eavesdropper cannot differentiate the messages sent by the queried tag from the ones sent by the noisy tag. Consequently, she is unable to identify the secret bits that are sent to the reader. Afterwards, the secret shared by the reader and the tag can be used to launch a secure channel in order to protect communications against eavesdroppers. It can also be used to securely refresh a tag's identifier by, for example, xoring the new identifier with the exchanged secret key. Refreshing tags' identifiers improves privacy since it prevents tracking tags. © IFIP International Federation for Information Processing 2006.