On Anonymity Communication And Electronic Cash

Computer networks especially Internet are widely used in the world. It has been greatly changing our daily life. The sender and receptor for a certain message should be kept secret in many applications. Anonymity communication is essentially needed in the digital world. Electronic payment systems are essential tools for E-commence. Electronic cash will play an important role in the future due to its unique anonymity property. There are many practical systems that provide anonymous communications for Internet users and electronic cash systems in operation after about 20 years academe study in the literature of anonymity communication and electronic cash. Mixes net technology is used as a basic tool in anonymity communication systems. eCashTM is the first employment electronic cash system in the world. We focus on the fields of anonymity communication and electronic cash in this dissertation. Our main contributions is listed as following: 1. An overview of current techniques, deployment and research project of anonymity communication is present; 2. A new method for measuring sender and receptor's unlinkabilty is given which can be used to judge a anonymity communication system; 3. A new (t,N-2)-resilience verifiable Mix net protocol is proposed using the primitive cryptography tools of Shamir secret share scheme, ElGamal public key system, zero-knowledge and so on . Its communication cost and computing cost is less than other verifiable Mix net that we know presently; 4. A secure electronic voting scheme based on the new Mix net is designed. Our scheme has the properties: vote privacy,fairness,publicity, voting public verifiability,and voter's anonymity simultaneously; 5. The notion, design, deployment and application of electronic cash is summarized. Some open problems in the field are present; 6. Two flaws in the eCashTM system are pointed out. A new improved applicable system for eCashTM is given that has the same efficiency with eCashTM and also overcomes the flaws; 7. An off_line revocable anonymity eCashTM like efficient applicable system is designed .