At Crypto 2015 Fuchsbauer, Hanser and Slamanig FHS presented the first standard-model construction of efficient round-optimal blind signatures that does not require complexity leveraging. It is conceptually simple and builds on the primitive of structure-preserving signatures on equivalence classes SPS-EQ. FHS prove the unforgeability of their scheme assuming EUF-CMA security of the SPS-EQ scheme and hardness of a version of the DH inversion problem. Blindness under adversarially chosen keys is proven under an interactive variant of the DDH assumption.#R##N##R##N#We propose a variant of their scheme whose blindness can be proven under a non-interactive assumption, namely a variant of the bilinear DDH assumption. We moreover prove its unforgeability assuming only unforgeability of the underlying SPS-EQ but no additional assumptions as needed for the FHS scheme.
['Georg Fuchsbauer', 'Christian Hanser', 'Chethan Kamath', 'Daniel Slamanig']
Practical Round-Optimal Blind Signatures in the Standard Model from Weaker Assumptions