Reassessing Security of Randomizable Signatures
The Camenisch-Lysyanskaya (CL) signature is a very popular tool in cryptography, especially among privacy-preserving constructions. Indeed, the latter benefit from their numerous features such as randomizability. Following the evolution of pairing-based cryptography, with the move from symmetric pairings to asymmetric pairings, Pointcheval and Sanders (PS) proposed at CT-RSA ’16 an alternative scheme which improves performances while keeping the same properties. Unfortunately, CL and PS signatures raise concerns in the cryptographic community because they both rely on interactive assumptions that essentially state their EUF-CMA security. This lack of precise security assessment is obviously a barrier to a widespread use of these signatures and a reason for preferring other constructions, such as the ones relying on q-type assumptions.