AnIntroductionToCryptography·Chapter3 45 Non-Repudiation Non-repudiation prevents an entity taking part in a data transaction from denying their participation in that transaction. In the previous examples in Figures 3.1 and 3.2, A will not be able to deny that he or she did not send the message when non-repudiation is incorporated into the cryptographic processes. Cryptographic Protocols and Applications Cryptography is used to secure data and information security, both when stored and in transit. This is achieved by using cryptographic applications and protocols. Cryptographic protocols are built on cryptographic algorithms and describe how an algorithm works. Cryptographic protocols are used in user applications or in developing other protocols. A cryptographic application or a protocol is a collection of cryptographic protocols, techniques, and methods combined with a user-friendly interface. While cryptographic algorithms and techniques are complex, these applications and protocols enable end users to achieve the benefits of cryptography without having to become proficient in the algorithms or the mathematics behind these algorithms. Following are some commonly used cryptographic protocols and applications. Domain Name Server Security Extensions