Combined Public-Key Schemes: The Case of ABE and ABS

Abstract

In the context of public key cryptography, combined encryption and signature schemes have attractive properties and are sometimes used in practice. The topic of joint security of signature and encryption schemes has a fairly extensive history. In this paper, we focus on the combined public-key schemes in attribute-based setting. We present a security model for combined CP-ABE and ABS schemes in the joint security setting. An efficient concrete construction of CP-ABE and ABS based on Waters's CP-ABE scheme is proposed. Our scheme is proved to be selectively jointly secure in standard model under reasonable assumptions. Moreover, we consider the problem of how to build attribute-based signcryption (ABSC) and obtain an ABSC scheme and show that it is secure. We also give a general construction of combined ABSC, CP-ABE and ABS schemes from combined CP-ABE and ABS schemes.