Efficient Round Optimal Blind Signatures.

Known constructions of blind signature schemes suffer from at least one of the following limitations: (1) rely on parties having access to a common reference string or a random oracle, (2) are not round-optimal, or (3) are prohibitively expensive. In this work, we construct the first blind-signature scheme that does not suffer from any of these limitations. In other words, besides being round optimal and having a standard model proof of security, our scheme is very efficient. Specifically, in our scheme, one signature is of size 6.5 KB and the communication complexity of the signing protocol is roughly 100 KB. An amortized variant of our scheme has communication complexity less that 1 KB.