RUNNING EXAMPLE
This protocol is a variant of the OSK protocol described in: M. Ohkubo, K. Suzuki, S. Kinoshita et al., “Cryptographic approach to “privacy-friendly” tags,” RFID privacy workshop, vol. 82. Cambridge, USA, 2003.
Each tag is associated to a mutable state sT initialized with s0. Readers have access to a database containing an entry sR for each authorized tag.
sT := H(sT,k) T -> R : G(sT,k’)
input x; sR := H(sR,k) if x = G(H(sR,k),k’) with sR in DB R -> T : ok
COMMENTS - In this model we add in parallel a process in order to provide the attacker the ability to compute hashes with their respective keys (without knowing these keys). - The reader process is not modelled here, this is left for future work.
HELPING LEMMAS - last update - disjoint chains - monotonic chain
SECURITY PROPERTIES - strong secrecy ******************************************************************************
The contents of distinct memory cells never coincide.
Values do not repeat inside the same chain of hashes.