### MoniPoly---An Expressive $q$-SDH-Based Anonymous Attribute-Based Credential System

Syh-Yuan Tan and Thomas Gross

##### Abstract

Modern attribute-based anonymous credential (ABC) systems benefit from special encodings that yield expressive and highly efficient show proofs on logical statements. The technique was first proposed by Camenisch and Groß, who constructed an SRSA-based ABC system with prime-encoded attributes that offers efficient AND, OR and NOT proofs. While other ABC frameworks have adopted constructions in the same vein, the Camenisch-Groß ABC has been the most expressive and asymptotically most efficient proof system to date, even if it was constrained by the requirement of a trusted message-space setup and an inherent restriction to finite-set attributes encoded as primes. In this paper, combining a new set commitment scheme and a SDH-based signature scheme, we present a provably secure ABC system that supports show proofs for complex statements. This construction is not only more expressive than existing approaches, it is also highly efficient under unrestricted attribute space due to its ECC protocols only requiring a constant number of bilinear pairings by the verifier; none by the prover. Furthermore, we introduce strong security models for impersonation and unlinkability under adaptive active and concurrent attacks to allow for the expressiveness of our ABC as well as for a systematic comparison to existing schemes. Given this foundation, we are the first to comprehensively formally prove the security of an ABC with expressive show proofs. Specifically, we prove the security against impersonation under the $q$-(co-)SDH assumption with a tight reduction. Besides the set commitment scheme, which may be of independent interest, our security models can serve as a foundation for the design of future ABC systems.

Available format(s)
Category
Cryptographic protocols
Publication info
A major revision of an IACR publication in ASIACRYPT 2020
Keywords
Contact author(s)
syh-yuan tan @ newcastle ac uk
thomas gross @ newcastle ac uk
History
2020-12-10: last of 2 revisions
See all versions
Short URL
https://ia.cr/2020/587

CC BY

BibTeX

@misc{cryptoeprint:2020/587,
author = {Syh-Yuan Tan and Thomas Gross},
title = {MoniPoly---An Expressive $q$-SDH-Based Anonymous Attribute-Based Credential System},
howpublished = {Cryptology ePrint Archive, Paper 2020/587},
year = {2020},
note = {\url{https://eprint.iacr.org/2020/587}},
url = {https://eprint.iacr.org/2020/587}
}

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