| dc.description.abstract | 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. | en_US |