Security analysis on "Strongly secure certificateless key-insulated signature secure in the standard model"

Certificateless signature eliminates the need of certificates in traditional public key signature and solves the inherent key escrow problem in identity-based signature. Therefore, it is an important secure requirement to solve key escrow problem in certificateless signature scheme, i.e., certificateless signature scheme should to resist the malicious but passive KGC attack. Key-insulated signature reduces the endangerment of private key leakage. Recently, Chen et al. propose a certificateless key-insulated signature scheme, and give the security proof in the standard model. In this paper, we give a security analysis of Chen et al.'s scheme. Our analysis reveals that Chen et al.'s scheme is vulnerable to the malicious-but-passive KGC attack.