Leakage-Resilient Certificateless Signcryption Scheme Under a Continual Leakage Model

Signature can be used to verify the integrity of both a message and the identity of a signer, whereas encryption can be used to ensure the confidentiality of a message. In the past, cryptography researchers have studied and proposed numerous certificateless signcryption (CLSC) schemes to combine the benefits of both signature and encryption. However, these schemes may not be robust enough to withstand side-channel attacks. Through such attacks, an attacker can constantly retrieve a portion of a private key of the system, and could eventually recover the entire private key. Leakage-resilient certificateless signcryption (LR-CLSC) can ensure its security when the attacker launches such attacks. As far as we know, the existing LR-CLSC schemes can only guarantee the security under a bounded leakage model, where the portion of the private key that an attacker can obtain through side-channel attacks is limited. In this paper, we propose the $first$ LR-CLSC scheme under a continual leakage model. Also, we demonstrate the proposed scheme is secure for the existential unforgeability and the ciphertexts indistinguishability against attackers with side-channel attacking abilities.