An efficient multi recipient signcryption scheme offering non repudiation

Signcryption was first proposed by Zheng and there after several signcryption schemes have been formulated. The broadcast scheme for Zheng does not offer non repudiation using public verification. A latest research by Elkamchouchi et. al proposed a new signcryption scheme for the broadcast environment. The scheme is known as Signcryption Multiple- Recipients Variant (SMRV). From the detail analysis of the scheme, it is observed that confidentiality of the information is lost when the parameters are sent to the third party for verification. Thus the scheme violates the basic property of security. Upon further analysis it is seen that the computational cost of the scheme can be reduced by eliminating few unnecessary steps which do not strengthen the security of the scheme but introduces an extra computational cost. In this paper an efficient and improved signcryption scheme for the broadcast environment is presented. The presented scheme is more efficient than Zheng's and Elkamchouchi et. al scheme in terms of computational cost. The scheme offers non repudiation through public verification and confidentiality of the information is also ensured.