Analysis and Enhance of Anonymous Signcryption Model

Ring signcryption, a cryptographic primitive to protect security and privacy, is an encryption and authentication scheme in a single logical step which allows a user to anonymously signcrypt a plaintext on behalf of a group of users that decrypter cannot know who is the actual signcrypter. In 2009, Zhang, Gao, Chen and Geng proposed a novel anonymous signcryption scheme(denoted as the ZGCG scheme) which is more efficient in computational cost and ciphertext length than the related schemes. In this paper, however, we show that the ZGCG scheme has not anonymity secure for the receiver, and then we propose an improved anonymous signcryption scheme that remedies the weakness of the ZGCG scheme. Our proposed scheme satisfies the semantic security, unforgeability, signcrypter identity’s ambiguity, and public authenticity. We also give the formal security proof in the random oracle model.