Attribute-based Signcryption with Ciphertext-policy and Claim-predicate Mechanism

We propose a new notion called attribute-based sign-cryption with cipher text-policy and claim-predicate mechanism (CP2-ABSC), which is inspired by the recent developments in attribute-based encryption and attribute-based signature. In this notion, a signcrypting party, who possesses a set of attributes from the authority, can sign a message with a claim-predicate that is satisfied by his attributes, and encrypt it with an access policy stating what kind of receivers will be able to decrypt the message. As in ciphertext-policy attribute-based encryption (CP-ABE), a user will only be able to decrypt a signcrypted message if that user´s attributes satisfy the access policy associated to the signcrypted message. As in attribute-based signature with claim-predicate mechanism (CP-ABS), a unsigncrypting party can verify the authenticity of the signcrypted message against the claim-predicate over signcrypting party´s attributes. We give the formal definition and security model of CP2-ABSC, and propose an CP2-ABSC construction from pairings which is more efficient than the combination of CP-ABE and CP-ABS that provide the same functionality of authenticated encryption. The proposed CP2-ABSC scheme is proved to be secure in the generic group model and random oracle model.