Cryptology ePrint Archive: Report 2016/662

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

Georg Fuchsbauer and Christian Hanser and Chethan Kamath and Daniel Slamanig

Abstract: 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.

Category / Keywords: cryptographic protocols / Blind Signatures, Standard Model, SPS-EQ

Original Publication (with major differences): SCN 2016

Date: received 28 Jun 2016

Contact author: christian hanser at iaik tugraz at

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Version: 20160628:211418 (All versions of this report)

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