Efficient revocation of security capability in certificateless public key cryptography

This paper presents the first mediated certificateless public key encryption and signature schemes. We also extend our schemes into hierarchical schemes. Our schemes does not suffer from the key escrow property that seems to be inherent in the mediated identity-based schemes. Key escrow is not always a good property for all applications because the exposure of a master key enable all the users' private keys to be leaked. Our mediated certificateless public key encryption and hierarchical schemes also support role based access control (RBAC) without the key escrow to manage the access to resources of a system. We finally describe security of our schemes and compare our schemes with the mediated identity based schemes from efficiency points of view.