Abstract:

That a presented proposal of efficient certificateless signature scheme is insecure against public key replacement attack is demonstrated. It is shown that an adversary who replaces the public key of a signer can forge valid signatures for the signer without knowledge of the signer’s private key. Then the scheme is improved by replacing the original public key with a public key pair. It enables a verifier to check the validity of a signer’s public key pair by simplifying the signature construction. The improved scheme is proven secure against existential forgery under the random oracle model.

Key words: certificateless signature, public key replacement attack, key escrow