A directed signature scheme based on rsa assumption

A directed signature scheme allows a designated verifier to directly verify a signature issued to him, and a third party to check the signature validity with the help of the signer or the designated verifier as well. Due to its merits, the directed signature scheme can be applied on some personally or commercially sensitive occasions. Up to now, there are several directed signature schemes having been proposed. However, to our best knowledge, none of them has provided the provable security proof. Therefore, in this paper, we would like to formally define the directed signature, and present a new directed signature scheme based on RSA assumption, then use the techniques from provable security to analyze the security of our proposed scheme.