Note: Cryptanalyzed in http://eprint.iacr.org/2009/298
The conventional public key cryptography model includes a central authority that issues certificates and manages a public key infrastructure, requiring significant processing and storage capabilities. Identity-based cryptography (ID-PKC) replaces the traditional public keys with identifiers derived from users’ identities. This facilitates public key validation but introduces the key escrow of private keys by the central authority as a side-effect. Certificateless cryptography (CL-PKC) is a novel paradigm where the generated costs are reduced without introducing key escrow of private keys. A signcryption scheme is a technique that provides confidentiality, authentication and non-repudiation in a single integrated operation. The first concrete CL-PKC signcryption scheme was proposed recently in [Barbosa and Farshim 2008]. We propose an efficient CL-PKC signcryption scheme that supports publicly verifiable signatures, and that is more efficient than the first protocol.