The Research of Off-line Electronic Cash Systems

• Main Authors: Kuo-Zhe Chiou, 邱國哲
• Other Authors: Sung-Ming Yen
• Format: Others
• Language: en_US
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/91820912318402815876

碩士 === 國立中央大學 === 資訊工程研究所 === 92 === On-line business has gradually become an important issue nowadays due to the tremendous growth of electronic commerce on Internet. Especially, electronic cash system is one of most popular research topics for paying electronically. Electronic cash system proposed by David Chaum makes electronic payment on Internet possible with anonymity, off-line, and unforgeability. However, malicious user can freely commit crimes by means of the property of anonymity. In consideration of preventing criminal activities, the anonymity revocation has become a desired requirement. Unfortunately, although anonymity revocation can protect electronic cash system from being misused, it makes the category of systems inefficient at the same time. In this thesis, some electronic cash systems with revocable anonymity are introduced. These systems prevent criminal activities by means of the two most common cryptographic techniques double-spending detection and tracing. However, these systems are inefficient and impractical. Then one very efficient electronic cash system is presented that it is possible to resolve the problem of efficiency of those revocable anonymity systems. We propose two electronic cash systems concerning about efficient issue. The first one takes advantage of hash function operation in PayWord to reduce the use of public key operations while maintaining the anonymity property. This system is very efficient because hash function operation is faster than public key operation. We propose a new blind signature which combines with batch cryptography to construct another electronic cash system. The main idea is that amortizing the expensive computation cost accross many coins. Moreover, in terms of ensuring the system from being misused, it provides double-spending detection and tracing capability. Finally, we suggest that the proposed system works with elliptic curve in terms of security, computational speed, and space requirement. Finally, the complete view of the system converted to elliptic curve cryptography are also provided.