| Summary: | 碩士 === 逢甲大學 === 資訊工程所 === 91 === Recently, many commercial transactions had become popular in Internet. The systems of electronic cash and voting need some kinds of digital signature which contain the property of anonymity. D. Chaum had proposed the first blind signature system in 1982. In his paper, there are two properties in blind signature: (1) Blindness (2) Unlinkability. Those properties were applied in lots of electronic payment systems.
However, some research about the safety of blind signature had been investigated by many researchers. They claimed that the anonymity might be used for crimes like “blackmailing” and “money laundering”. For this reason, M. Stadler(1996) et al. showed the concept of fair blind signature and displayed three different kinds of schemes. They added the role of “The Third Trust Party” into the blind signature schemes to prevent those illegal behaviors.
But in real life, an ideal “Third Trust Party” may not be in existence. In our paper, a new fair blind signature scheme is proposed. In this scheme, the judge cannot trace the requester and extract the blind signature by itself. It means that the judge must be cooperated with the signer. Besides of these, the judge can not recover the message while the requester has encrypted it.
Accordingly, we eliminate the possibility of the requester cheating the judge to make the scheme safer and useful in applying it to the electronic cash systems.
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