The paper presents new protocols for two parties to exchange documents fairly, ensuring that neither party can gain an advantage by quitting prematurely or misbehaving. The protocols use a "semi-trusted" third party, which can misbehave but will not conspire with either of the main parties. The solutions are efficient and can be based on various cryptographic assumptions. The authors discuss the application of these techniques to electronic commerce protocols, particularly for fair payment. The paper includes a detailed description of the protocols, their correctness, and optimizations, as well as variations and applications to electronic payment schemes. The protocols ensure that disruption by any party does not allow the disrupter to gain useful information about the documents being exchanged.The paper presents new protocols for two parties to exchange documents fairly, ensuring that neither party can gain an advantage by quitting prematurely or misbehaving. The protocols use a "semi-trusted" third party, which can misbehave but will not conspire with either of the main parties. The solutions are efficient and can be based on various cryptographic assumptions. The authors discuss the application of these techniques to electronic commerce protocols, particularly for fair payment. The paper includes a detailed description of the protocols, their correctness, and optimizations, as well as variations and applications to electronic payment schemes. The protocols ensure that disruption by any party does not allow the disrupter to gain useful information about the documents being exchanged.