Provably Secure Certificate-based Proxy Signature Schemes

In this paper, we first propose the definition and security model of certificate-based proxy signature (CBPS). We then show that the certificate-based proxy signature scheme presented by Kang, Park and Hahn in CT-RSA 2004 are insecure against key replacement attacks. We further propose two certificate-based proxy signature schemes, which are shown to be existentially unforgeable against adaptive chosen message attacks under the computational Diffie-Hellman assumption in the random oracle model. Compared with the certificate-based proxy signature scheme in CT-RSA 2004, one of our schemes enjoys the same signature length and computation cost, another one requires a little more computation and communication cost.