Designated Verifier Proxy Signature Scheme

The work of this paper aims at an Improved Nominative Proxy Signature Scheme, which overcome the weakness of other Nominative Proxy Signature Scheme. Our scheme is more secure and efficient.Digital signature is one of the most important techniques in modern information security system for its functionality of providing data integrity and authentication. In a proxy signature scheme, an original signer delegates a user called proxy signer to sign message on behalf of the original signer. Since its introduction proxy signature has abstracted a great deal of interest. Now proxy signatures have found numerous applications, particularly in distributed computing, which include mobile agent application, mobile communication, and electronic voting, etc. Various proxy signature schemes have been presented, such as threshold proxy signatures, one-time proxy signatures, multi-proxy signature, proxy multi-signature, proxy blind signature, and proxy anonymous proxy signatures.Recently, Park and Lee proposed a nominative proxy signature scheme for mobile communication. The nominativc proxy signature scheme is a method in which the designated proxy signer generates a nominative signature and transmits it to a verifier, instead of the original signer. In the nominative proxy signature scheme for mobile communication, the mobile user acts as the original signer and the agent entity acts as the proxy signer. It is a useful method in the mobile communication environment, because it provides mobile users' anonymity through the nominative signature and decreases the mobile users' computational cost through the proxy signature. But, their scheme does not provide non-repudiation, even though they claimed that their scheme provides it. So, the original signer or proxy signer can falsely deny later the fact that he generated the signature. Therefore a dispute between the original signer and the proxy signer may be happened frequently.In this paper, we first analyze Park-Lee' s nominative proxy scheme and point out the problem of Park-Lee' s scheme; i. e., unlike their claim, the scheme does not satisfy non-repudiation, and Park-Lee' s nominative...