Groth-Sahai Proofs Revisited Again: A Bug in ``Optimized'' Randomization

Keita Xagawa

Paper 2016/476

Groth-Sahai Proofs Revisited Again: A Bug in ``Optimized'' Randomization

Keita Xagawa

Abstract

The Groth-Sahai proof system (EUROCRYPT 2008, SIAM Journal of Computing 41(5)) provides efficient non-interactive witness-indistinguishable (NIWI) and zero-knowledge (NIZK) proof systems for languages over bilinear groups and is a widely-used versatile tool to design efficient cryptographic schemes and protocols. We revisit randomization of the prover in the GS proof system. We find an unnoticed bug in the ``optimized'' randomization in the symmetric bilinear setting with several assumptions, say, the DLIN assumption or the matrix-DH assumption. This bug leads to security issues of the GS NIWI proof system with ``optimized'' randomization for multi-scalar multiplication equations and the GS NIZK proof system with ``optimized'' randomization for certain cases of pairing product equations and multi-scalar multiplication equations.

Metadata

Available format(s): PDF
Category: Cryptographic protocols
Publication info: Preprint. MINOR revision.
Keywords: Non-interactive proof systems the Groth-Sahai proof system symmetric bilinear groups the DLIN assumption
Contact author(s): xagawa keita @ lab ntt co jp
History: 2016-05-20: revised; 2016-05-19: received; See all versions
Short URL: https://ia.cr/2016/476
License: CC BY

BibTeX

@misc{cryptoeprint:2016/476,
      author = {Keita Xagawa},
      title = {Groth-Sahai Proofs Revisited Again: A Bug in ``Optimized'' Randomization},
      howpublished = {Cryptology {ePrint} Archive, Paper 2016/476},
      year = {2016},
      url = {https://eprint.iacr.org/2016/476}
}