Secure universal designated verifier signature without random oracles

In Asiacrypt 2003, the concept of universal designated

verifier signature (UDVS) was introduced by

Steinfeld, Bull, Wang and Pieprzyk. In the new paradigm,

any signature holder (not necessarily the signer) can designate

the publicly verifiable signature to any desired designated

verifier (using the verifierÿs public key), such that only

the designated verifier can believe that the signature holder

does have a valid publicly verifiable signature, and hence,

believes that the signer has signed the message. Any other

third party cannot believe this fact because this verifier can

use his secret key to create a valid UDVS which is designated

to himself. In ACNS 2005, Zhang, Furukawa and Imai

proposed the first UDVS scheme without random oracles. In

this paper,we give a security analysis to the scheme of Zhang

et al. and propose a novel UDVS scheme without random

oracles based on Watersÿ signature scheme, and prove that

our scheme i