Date Added: Oct 2012
Signcryption is a cryptographic primitive that fulfill the functionalities of digital signature and public key encryption simultaneously, at a cost significantly lower than that required by the traditional sign-then-encrypt or encrypt-then-sign approach. In this paper, the authors address the question whether it is feasible to construct a PKI based signcryption scheme with tight security reduction in the insider security model of signcryption without pairing. This question seems to have never been addressed in the literature before. They answer the question positively in this paper. They give a novel PKI based signcryption scheme and the security is based on CDH- assumption. Ours is the first scheme of its kind which is secure in insider security model proved with tight security reduction.