Electronic cash protocol with anonymity withdrawal under a third party supervision

Attributes of an electronic cash system which is brought up in paper are analyzed. The system based on limited blind signature is pointed out that it isn´t satisfied with atomicity. At the same time this system also doesn´t meet the fair anonymity in some degree. These defects are improved by imposing a trustable third trust part(TTP)to control the whole transaction. Then a new electronic cash protocol is brought up. And a signed user´s identity information is embedded by TTP in cash, thus user´s anonymity will be withdrawn by TTP when he breaks the law. So the safety of transaction is ensured.