Threshold Attribute-Based Signcryption in Standard Model

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 signcrytion (ABSC) which simultaneously achieves the functionalities of attribute-based encryption (ABE) and attribute-based signature (ABS), 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 attribute-based signcryption (TABSC) scheme. The scheme is proven secure under the well-established Decisional Bilinear Diffie-Hellman (DBDH) and the standard Computational Diffie-Hellman (CDH) assumptions in the standard model. Compared with the state of the ABSC art, our scheme has comparable efficiency without relying on any random oracle.