Insecurity of a Secure Certificate-Based Signature Scheme

Certificate-Based Signature (CBS) not only provides the solution of certificate revocation problems arise in the traditional public key cryptography but also solve key escrow problem arise in ID Based signature scheme. Recently, Hung et al’s design an efficient short certificate based signature scheme (SCBS) using bilinear pairing publish in "Information Technology and Control", T. 45, Nr. 3 in 2016 and proves that it is safe against type 1 and type 2 adversaries under the computational Diffie-Hallmen (CDH) assumption. In this paper, we show that Hung et al’s scheme is not protected against an adversary who has no need of secret value and partial private key to forge the legal signature.