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

• Published in: Security and Cryptography for Networks pp. 391 - 408
• Main Authors: Fuchsbauer, Georg, Hanser, Christian, Kamath, Chethan, Slamanig, Daniel
• Format: Book Chapter
• Language: English
• Published: Cham Springer International Publishing 2016
• Series: Lecture Notes in Computer Science
• Subjects: Blind Signature; Blind Signature Scheme; Common Reference String; Random Oracle; Signature Scheme
• ISBN: 9783319446172; 3319446177
• ISSN: 0302-9743; 1611-3349
• DOI: 10.1007/978-3-319-44618-9_21

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. 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.