Identity-Based Parallel Key-Insulated Proxy Signature in the Random Oracle Model

Exposure of private keys is harmful to the public key cryptosystems. In this paper, an identity-based parallel key-insulated proxy signature (IBPKIPS) scheme is given to solve the problem of proxy signing key exposure in the identity-based proxy signature system. The IBPKIPS scheme is secure in the random oracle model. Two different helper keys are used to refresh the temporary proxy signing keys in the scheme. The proposed scheme is more flexible than the IBPKIPS scheme in the standard model.