Improved Hidden identity-based signature scheme

In Financial Cryptography 2007, Kiayias and Zhou introduced a novel concept of Hidden identity-based signatures (abbreviated as Hidden-IBS) by adapting the traditional notion of group signatures. Compared with existing group signature schemes, Hidden-IBS is more desirable in some applications, such as identity-information management systems and anonymous credential systems. At the same time, Kiayias and Zhou firstly proposed the Hidden-IBS from bilinear pairings. Unfortunately, the Kiayias-Zhou scheme fails to achieve exculpability and CCA2-anonymity, which are commonly agreed properties for group signature scheme and Hidden-IBS. In this paper, an improved Hidden-IBS is proposed by employing the techniques of the Sigma-compiler for concurrent zero knowledge argument and a variant of Cramer-Shoup encryption based on the linear assumption. The new scheme enjoys the advantages of strengthened security, concurrent join and desirable properties in performance, especially in the signature length. Moreover, in order to alleviate the expensive pairing operations of the verifier, an efficient batch verification algorithm is also provided.