Identity-based parallel key-insulated signature without random oracles

We extend Hanaoka et al.'s parallel key-insulated mechanism to identity-based signature scenarios, and propose an identity-based parallel key-insulated signature scheme. The proposed scheme enjoys several attractive features: (i) it is provably secure without random oracles; (ii) it is strong key-insulated, and even if one of a user's helper key and some of his temporary secret keys are exposed, it is still impossible for an adversary to derive all of this user's temporary secret keys; (iii) it allows frequent key-updates without increasing the risk of helper key-exposure, and thus enhances the security of the system.