Provably secure and efficient leakage-resilient certificateless signcryption scheme without bilinear pairing

The signcryption scheme should withstand various leakage attacks in practical applications. This paper presents a new leakage-resilient certificateless signcryption (LR-CLSC) scheme without bilinear pairing. The security of this scheme is based on the computational Diffie-Hellman (CDH) assumption and discrete logarithm (DL) problem. Considering the computational costs, our proposed method is more efficient than traditional certificateless signcryptions schemes and has a short ciphertext length and high security. In the random oracle model, the proposed approach is semantically secure against adaptive posteriori chosen-ciphertext key-leakage attacks (IND-KL-CCA2) according to the hardness of the CDH assumption, and existentially unforgeable against chosen-message key-leakage attacks (EUF-KL-CMA) according to the hardness of the DL problem. Furthermore, it will maintains the original security under the condition that the adversary learns a small amount of leakage information about the secret key by the side channel attacks. The key leakage parameter λ and message length m are subject to λ≤logq−m−2log(1ω). Given that a dependence between λ and m is undesirable, a new variant that also against IND-KL-CCA2 and EUF-KL-CMA is presented. With a leakage resilient length of up to λ≤logq−2log(1ω), the leakage parameter λ has a constant size which is independent of the message length m. Our proposed method is the first LR-CLSC scheme with an independent leakage parameter and it can be applied into mobile internet.