Controlled proxy re-signing - conditional proxy re-signatures

Delegation of authentication is one of the vital security management strategies to manage device authentication in an enormous network. Major issue while delegating authentication using traditional proxy cryptography is that the delegator loses control over the messages which are authenticated by the delegatee and in proxy recryptography controlling the proxy from resigning unintended signatures of the delegatee is not possible. To address this concern, we propose a useful delegation scheme called as conditional proxy re-signature. In this paper, we propose a security model for unidirectional conditional proxy re-signature, present a concrete scheme and prove the security of the scheme in the random oracle model.