Practical Round-Optimal Blind Signatures in the Standard Model from Weaker Assumptions

Georg Fuchsbauer (1) , Christian Hanser (2) , Chethan Kamath (3) , Daniel Slamanig (2)

1 CASCADE - Construction and Analysis of Systems for Confidentiality and Authenticity of Data and Entities
2 TU Graz - Graz University of Technology [Graz]
3 IST Austria - Institute of Science and Technology [Klosterneuburg, Austria]

At Crypto'15 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. 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.

Domaines: Cryptographie et sécurité [cs.CR]

Georg Fuchsbauer, Christian Hanser, Chethan Kamath, Daniel Slamanig. Practical Round-Optimal Blind Signatures in the Standard Model from Weaker Assumptions. Security and Cryptography for Networks - 10th International Conference, SCN 2016, Aug 2016, Amalfi, Italy. ⟨10.1007/978-3-319-44618-9_21⟩. ⟨hal-01384381⟩