An Improved Certificateless Signcryption in the Standard Model

Signcryption is a cryptographic primitive which can offer simultaneously security requirements of confidentiality and authentication, and is more efficient than the traditional sign-then-encrypt way. Recently, Liu et al. proposed the first certificateless signcryption scheme in the standard model. However, their scheme is proved to have some security weaknesses. In this paper, we propose a corrected version of Liu et al.’s scheme and prove our scheme is indistinguishable against adaptive chosen ciphertext attacks and is existentially unforgeable against chosen message attacks in the standard model. Performance analysis shows the new scheme has smaller public parameter size than the previous certificateless signcryption schemes without using the random oracles.