A certificate-based proxy cryptosystem with revocable proxy decryption power

We present a proxy cryptosystem based on a certificate-based encryption scheme. The proposed scheme inherits the merits of certificate-based encryption systems: no-key-escrow and implicit certification. In addition, the proposed scheme allows the proxy's decryption power to be revoked even during the valid period of the proxy key without changing the original decryptor's public information. Few proxy schemes have this property, and ours is more efficient than the existing ones. We show that our proposal is IND-CBPd-Rev-CCA secure under the bilinear Diffie-Hellman assumption in the random oracle model.