Efficient Construction of Identity Based Signcryption Schemes from Identity Based Encryption and Signature Schemes

In this paper, we show how to construct an Identity Based Signcryption Scheme (IBSC) using an Identity Based Encryption (IBE) and an Identity Based Signature (IBS) schemes. This we obtain by first extending the An-Dodis-Rabin construction to the Identity Based setting and then instantiating. We then further modify the construction to obtain an efficient construction. We show that the security of the IBSC scheme–indistinguishability as well as unforgeablity–is derived from the security of the underlying IBE and IBS schemes. Moreover, we show that under mild (reasonable) assumptions, the scheme is both space and time efficient compared to the Sign-then-Encrypt approach.