The Research And Application Of Integrated Digital Signature

Digital signature is an important service that contemporary cryptography provides. It is foundation of mutual trust in the Internet; also, it is the key technique of putting e-government and e-commerce into practice successfully and generally. It is used for the proof of author identity, because it has the following properties:(1) Signature is trusted. It makes the receiver of document believe that signer signed on the document discreetly.(2) Signature cannot be forged. Signature proves it is the signer not other persons signed on the document.(3) Signature cannot be reused. Signature is part of document. Attacker cannot divert the signature to different document.(4) Signature cannot be changed. After signing, the document cannot be changed.(5) Signature is undeniable. Signature and document are physical materials. The signer cannot deny that he has signed on it.Electronic signature is extensively applicable in various surroundings and ways. Accordingly, many different types of signatures have been developed to apply to varied application surroundings and ways during the past two decades. However, ways and structures of Internet communication become more and more complicated. Therefore, there are more and more cryptographic services each of which needs the aid of several different types of signature. For example, in a robust electronic payment system, blind signature, undeniable signature, and multi-signature should be all indispensable. In this situation, if independently different signature schemes are used, it may cause extremely enormous computation cost, for the parameters and modulus used in different schemes could be quite different. In addition, it may lower the practical efficiency of the system, Accordingly, the problem of designing an integrated system that will simultaneously provide service of several different types of signatures is the very significant research issue to contemporary cryptography, and needed to solve it as soon as possible. In this thesis, I propose the first concept of integrated signature and concentrate ourselves on the design of an integrated signature scheme that has the following engaging properties:(1) It is both a blind signature and a weakly undeniable signature.(2) The modulus used by each participant cosigner is identical.(3) It is identical in form to a standard RSA signature.(4)The length of the signature is independent of the number of participant cosigners.(5)The unforgeability of the scheme is equivalent to an ordinary RSA signaturescheme.Being a multisignature, the power and responsibility of the signer can be distributedly shared by a set of cosigners. Being blind and unlinkable, the privacy as well as anonymity of the signature requester is protected. Further, being weakly undeniable, it protects the signers and gives them more control over the verification of the signature. Accordingly, the suggested scheme is more suitable for many important cryptographic services, such as secure electronic voting service, electronic payment service and other electronic commerce service etc, than an ordinary signature scheme. Therefore, based upon the suggested weakly undeniable and blind multisignature scheme, I also develop a secure multiauthority Internet bidding system in order to prevent possible cheating from a single authority system. The Camenish-Staeller group signature is used for registing the members when our signature is used for electronic bid.