Key Replacement Attack on a Certificateless Signature Scheme

Yap, Heng and Goi propose an efficient certificateless signature scheme based on the intractability of the computational DiffieHellman problem, and prove that the scheme is secure in the random oracle model. This paper shows that their certificateless signature scheme is vulnerable to key replacement attacks, where an adversary who replaces the public key of a signer can forge valid signatures on any messages for that signer without knowing the signer’s private key.