Towards Confidentiality of ID-Based Signcryption Schemes under without Random Oracle Model

Abstract

Signcryption, achieves confidentiality and authenticity simultaneously in an efficient manner, is a novel cryptographic primitive in a single logic step with more efficient computation and communication cost to support the security. In this paper, we analyze two identity based signcryption schemes under the without random oracles model including a signcryption scheme by Yu et al. [11] and a certificateless signcryption scheme by Liu et al. [12]. We give the chosen plaintext attacks to prove that the proposed previous schemes cannot resist on the indistinguishability on chosen ciphertext attack to support semantic secure for confidentiality.