Weaknesses in a recent Ultra-Lightweight RFID Authentication Protocol

In this paper we show weaknesses in SASI, a new Ultra-Lightweight RFID Authentication Protocol, designed for providing Strong Authentication and Strong Integrity. We identify three attacks, namely, a de-synchronisation attack, through which an adversary can break the synchronisation between the RFID Reader and the Tag, an identity disclosure attack, through which an adversary can compute the identity of the Tag, and a full disclosure attack, which enables an adversary to retrieve all secret data stored in the Tag. The attacks are effective and efficient.