Fully-Anonymous Short Dynamic Group Signatures Without Encryption.

摘要: Group signatures are a central tool in privacy-enhancing crypto, which allow members of group to anonymously sign on behalf the group. Ideally, dynamic and thus dynamically enroll new For such schemes Bellare et al. (CT-RSA’05) proposed strong security model (BSZ model) that preserves anonymity signature even if an adversary can see arbitrary key exposures or openings other signatures. All previous constructions achieving this notion follow so called sign-encrypt-prove (SEP) paradigm. In contrast, all known avoid paradigm alternative “without encryption” introduced by Bichsel (SCN’10), only provide weaker (which be problematic practice). Until now, it was not clear following paradigm, while providing sense BSZ, exist. paper we positively answer question novel approach is composition structure preserving equivalence classes (Asiacrypt’14) standard primitives. Our results interesting for various reasons: We prove our construction secure without requiring random oracles. Moreover, when opting instantiation ROM, obtained scheme extremely efficient outperforms existing fully anonymous SEP regarding computational efficiency. Regarding than surprisingly outperform popular short BBS (Crypto’04) thereby obtain shorter