Cryptology ePrint Archive: Report 2019/284

Proper Usage of the Group Signature Scheme in ISO/IEC 20008-2

Ai Ishida and Yusuke Sakai and Keita Emura and Goichiro Hanaoka and Keisuke Tanaka

Abstract: In ISO/IEC 20008-2, several anonymous digital signature schemes are specified. Among these, the scheme denoted as Mechanism 6, is the only plain group signature scheme that does not aim at providing additional functionalities. The Intel Enhanced Privacy Identification (EPID) scheme, which has many applications in connection with Intel Software Guard Extensions (Intel SGX), is in practice derived from Mechanism 6. In this paper, we firstly show that Mechanism 6 does not satisfy anonymity in the standard security model, i.e., the Bellare-Shi-Zhang model [CT-RSA 2005]. We then provide a detailed analysis of the security properties offered by Mechanism 6 and characterize the conditions under which its anonymity is preserved. Consequently, it is seen that Mechanism 6 is secure under the condition that the issuer, who generates user signing keys, does not join the attack. We also derive a simple patch for Mechanism 6 from the analysis.

Category / Keywords: public-key cryptography / Group signature, Cryptanalysis, ISO/IEC 20008-2, SGX

Date: received 12 Mar 2019

Contact author: a ishida at aist go jp

Available format(s): PDF | BibTeX Citation

Version: 20190316:211350 (All versions of this report)

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