Threshold Attribute-Based Signcryption And Its Application To Authenticated Key Agreement

Signcryption is a kind of modern cryptosystem that can implement with digital signature and public key encryption in one algorithm structure, and its calculation and communication costs are extremely lower than the previous signature-then-encryption protocol. Due to its importance and efficiency, the task of constructing efficient and secure signcryption protocol has attracted a lot interests. With the rapid development of internet technology and cloud computing service platform, the signcryption schemes with additional func-tional properties are playing an irreplaceable role in many different application environments, especially in the background of the big data era. Although some signcryption protocols with additional functional properties has been proposed, research on attribute-based signcrytion (ABSC) is not much. The public key of the user is generated relying on his attribute sets in attribute-based signcrytion scheme. This scheme satisfies the attribute characteristics of attribute-based encryption (ABE) and attribute-based signature (ABS) simultaneously, which are two very important cryptographic techniques in cloud computing access control and user authentication. So the research on attribute-based signcry-tion is one of the development trends of cloud computing security in the future.In this thesis, we present a threshold attribute-based signcryption scheme (TABSC). The construction of this protocol is based on bilinear pairing and the lagrange interpolation algorithm. The security of this constructed scheme is based on 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 in standard model, our scheme not only possesses message confidentiality and unforgeability, but also is more efficient in the practical application and takes less communication costs because of its concise structure without using random oracles and less bilinear pairing calculation in the operation of the protocol.Furthermore, based on further study on the attribute-based signcryption (ABSC) and key agreement protocols, we construct an authenticated key a-greement protocol based on this threshold attribute-based signcryption from the point of improving the security of cloud computing. This protocol satisfies the security attributes in the key agreement system, and extends the applica-tion of ABSC in key agreement.