An Improved Certificateless Generalized Signcryption Scheme

Abstract

Signcryption is basically a cryptographic primitive which provides both signature and encryption functions simultaneously, but it is not useful when only one of the function is required. Generalized Signcryption (GSC) is a special cryptographic primitive which can provide Signcryption function when security and authenticity are needed simultaneously, and can also provide encryption or signature function separately when any one of them is needed. The first Generalized Signcryption was proposed in 2006 by Han et al. Since then many Generalized Signcryption has been proposed based on ECDLP, based on Bilinear Pairing, Identity based and some are also proposed in Certificateless environment. Majority of the Generalized Signcryption schemes uses Random Oracle Model for their security proof and few are proposed based on Standard model. In this thesis we have surveyed the existing GSC schemes and compare their security properties and efficiency. Along with this we also have proposed two schemes of which first one is an Identity based Generalized Signcryption Scheme and second one is a Certificateless Generalized Signcryption Scheme which is a variation of Certificateless Signcryption Scheme by Barbosa et al. We begin by giving formal definition of GSC primitive and complete with comparative study with other models. Finally, we look ahead at what future progress might be made in the field.