Identity-based encryption with forward security

Standard identity-based encryption schemes typically rely on the assumption that secret keys are kept perfectly secure. However, with more and more cryptographic primitives are deployed on insecure devices, key exposure seems inevitable. In this paper, we propose an Identity-based encryption scheme with forward security. In the scheme, secret keys are updated at regular periods of time; furthermore, exposure of a secret key corresponding to a given time period does not enable an adversary to break the scheme for any prior time period. The scheme achieves security against chosen ciphertext attacks under the bilinear Diffie-Hellman assumption in the random oracle model.