An Expressive Attribute-based Signature Scheme without Random Oracles

Attribute-based signatures (ABS) is a new cryptographic primitive and can play a great role in attributebased access control systems. In ABS, a signer can choose its attributes satisfying a policy of a verifier to generate a valid signature without reveal its identity or attributes, while the signature assures that the message is endorsed by an individual owning attributes the policy requiring. However, most existing works of ABS need random oracles, which is unpractical and results in the dependence of security on hash functions. In this paper, we refer to the mature techniques used in identity-based encryption (IBE) to propose an ABS scheme without random oracles. Our scheme support any expressive policy consisting of AND, OR, threshold gates, which offers great flexibility to the implementation of access control. Keywords-ABS;random oracles; policy; IBE