Certificateless online/offline signcryption scheme

Signcryption is a highly efficient approach to achieve simultaneously confidentiality and authentication of message, which is more feasible than the simple combination of encryption and signature. The online/offline cryptography can further enhance the efficiency of signcryption system process without affecting its security. At present, most online/offline signcryptions focus on the ID-based setting. However, the key escrow problem is inherent in ID-based cryptography, which is regarded as the main barrier to affect the implementation of system. In this paper, we propose a brand new certificateless online/offline signcryption scheme. We prove the security of our scheme under q-mBDHI, CDH and q-CAA assumptions in the random oracle model. The proposed scheme overcomes the key escrow problem in the ID-based setting. Copyright (c) 2014 John Wiley & Sons, Ltd.