Toward Efficient Certificateless Signcryption from (and without) Bilinear Pairings

cient certificateless signcryption scheme. Contrary to the usual paradigm of converting identitybased encryption and signature schemes into a combined certificateless protocol, we adopt the approach of extending a conventional signcryption method with a certificateless key validation mechanism, resorting to the underlying identity-based techniques, and as a onsequence to pairings, exclusively to validate the associated public keys. The result is as ecient as the underlying signcryption method as long as the amortized cost of this validation is low, as is the case of our concrete proposal.

In this paper we describe how to construct an e