Round Optimal Blind Signatures

Round Optimal Blind SignaturesD. Schröder, D. Unruh, S. Garg, V. Rao, and A. Sahai (Crypto 2011).  [publisher's version]

Abstract: Constructing round-optimal blind signatures in the standard model has been a long standing open problem. In particular, Fischlin and Schröder recently ruled out a large class of three-move blind signatures in the standard model (Eurocrypt'10). In particular, their result shows that finding security proofs for the well-known blind signature schemes by Chaum, and by Pointcheval and Stern in the standard model via black-box reductions is hard. In this work we propose the first round-optimal, i.e., two-move, blind signature scheme in the standard model (i.e., without assuming random oracles or the existence of a common reference string). Our scheme relies on the Decisional Diffie Hellman assumption and the existence of sub-exponentially hard 1-to-1 one way functions. This scheme is also secure in the concurrent setting.

Merger of Schröder, Unruh, Round Optimal Blind Signatures, 2011 and "Round Optimal Blind Signatures in the Standard Model" by Sanjam Garg, Vanishree Rao, and Amit Sahai.