The PHOTON Family of Lightweight Hash Functions
RFID security is currently one of the major challenges cryptography has to face, often solved by protocols assuming that an on-tag hash function is available. In this paper, the authors present the PHOTON lightweight hash-function family, available in many different flavors and suitable for extremely constrained devices such as passive RFID tags. Their proposal uses a sponge-like construction as domain extension algorithm and an AES-like primitive as internal unkeyed permutation. This allows them to obtain the most compact hash function known so far (about 1120 GE for 64-bit collision resistance security), reaching areas very close to the theoretical optimum (derived from the minimal internal state memory size).