Threshold attribute-based signcryption and its application to authenticated key agreement

Signcryption is a public key cryptosystem that achieves the functions of digital signature and public key encryption simultaneously. It significantly reduces the cost of traditional signature-then-encryption approach. Although a large body of signcryption schemes have been proposed, few works have been done on attribute-based signcryption (ABSC), which simultaneously achieves the functionalities of attribute-based encryption and attribute-based signature, two important cryptographic primitives proposed to enforce fine-grained access control and user authentication in cloud computing applications. In this paper, we present a threshold ABSC scheme. The scheme is proven secure under the well-established Decisional Bilinear Diffie–Hellman and the standard Computational Diffie–Hellman assumptions in the standard model. Compared with the state of the ABSC art, our scheme has comparable efficiency without relying on any random oracle. Furthermore, we construct an authenticated key agreement protocol based on this threshold attribute-based signcryption from the point of improving the security of cloud computing.