Provable secure protected designated proxy signature with revocation

In this paper, we present a novel concept in proxy signature by introducing a trusted proxy agent called mediator together with a proxy signer, which enables an efficient revocation of signing capability within the delegation period, by controlling the signing capability of proxy signer even before/after generating the signature by the designated proxy signer. We describe a secure designated proxy signature scheme with revocation based on elliptic curve discrete logarithmic problem. Further, we define a random oracle based security model to prove the security of the proposed scheme under an adaptive-chosen-message attack and an adaptive-chosen-warrant attack.