Group Signature with Deniability: How to Disavow a Signature

  • Ai Ishida
  • Keita Emura
  • Goichiro Hanaoka
  • Yusuke Sakai
  • Keisuke Tanaka
Conference paper

DOI: 10.1007/978-3-319-48965-0_14

Volume 10052 of the book series Lecture Notes in Computer Science (LNCS)
Cite this paper as:
Ishida A., Emura K., Hanaoka G., Sakai Y., Tanaka K. (2016) Group Signature with Deniability: How to Disavow a Signature. In: Foresti S., Persiano G. (eds) Cryptology and Network Security. CANS 2016. Lecture Notes in Computer Science, vol 10052. Springer, Cham

Abstract

Group signatures are a class of digital signatures with enhanced privacy. By using this type of signature, a user can sign a message on behalf of a specific group without revealing his identity, but in the case of a dispute, an authority can expose the identity of the signer. However, it is not always the case that we need to know the specific identity of the signature. In this paper, we propose the notion of deniable group signature, where the authority can issue a proof showing that the specified user is NOT the signer of the signature, without revealing the actual signer. We point out that existing efficient non-interactive zero-knowledge proof systems cannot be straightforwardly applied to prove such a statement. We circumvent this problem by giving a fairly practical construction through extending the Groth group signature scheme (ASIACRYPT 2007). In particular, a denial proof in our scheme consists of 96 group elements, which is about twice the size of a signature in the Groth scheme. The proposed scheme is provably secure under the same assumptions as those of the Groth scheme.

Keywords

Group signature Deniability Non-interactive zero-knowledge proof Bilinear map 

Copyright information

© Springer International Publishing AG 2016

Authors and Affiliations

  • Ai Ishida
    • 1
    • 2
  • Keita Emura
    • 3
  • Goichiro Hanaoka
    • 2
  • Yusuke Sakai
    • 2
  • Keisuke Tanaka
    • 1
    • 4
  1. 1.Tokyo Institute of TechnologyTokyoJapan
  2. 2.AISTTokyoJapan
  3. 3.NICTTokyoJapan
  4. 4.JST CRESTTokyoJapan