Abstract
Confidentiality and message authentication are the most important security goals that can be achieved simultaneously by Signcryption scheme. It is a cryptographic technique that performs both the functions of digital signature and public key encryption in a single logical step significantly at a lower cost than that of conventional method of signature-then-encryption. The paper proposes an efficient Certificateless Signcryption Scheme (CLSC) in random oracle model on bilinear mapping. It is provably secure under the assumptions of intractability of k-CAA, Inv-CDH, q-BDHI and CDH problems.