基于离线条件可信第三方的挂号邮件协议

扩展了半可信第三方的思想，提出条件可信第三方，给出可接受的第三方必须满足的条件，并结合离线可信第三方提出一个基于离线条件可信第三方的挂号邮件协议，目的是在保证可接受的公平结果的前提下尽可能减少对可信第三方的依赖；新协议在离线可信第三方介入的情况下能够达到可接受的公平结果；而且协议中的证据是第三方可验证的，未使用特殊的签名和加密技术，具有较好的适用性。

A New Protocol for Certified Mail Based on Off-line Conditional TTP

Electronic mail delivery is one of the most important and desirable services, by which the intended recipient will get the mail if and only if the mail originator receives a valid and irrefutable proof of the receipt. The idea of conditional trusted third party has been developed on the basis of semi-trusted TTP and a suite of acceptable conditions is given. A new practical protocol for certified e-mail is presented, which can guarantee acceptable fair with interception of conditional TTP. More, the evidence in the new protocol is publicly verifiable without any restrictions on the type of signature and encryption algorithms.