Non-repudiation is a service used in cybersecurity to provide assurance of the integrity and origin of data in such a way that the integrity and origin can be verified and validated by both the sender and the recipient. It is a legal concept that ensures that no party can deny that it sent or received a message via encryption and/or digital signatures or approved some information. Non-repudiation provides proof of the origin, authenticity, and integrity of data, and it verifies the sender that the information is sent and the recipients identity to the receiver.

Non-repudiation is achieved through cryptography, such as digital signatures, and includes other services for authentication, auditing, and logging. It can be accomplished in various ways, such as the digital signing of log data as a checksum during collection or using secured storage media. Non-repudiation combines both authentication and integrity, and it is like authentication, particularly with respect to implementation.

Non-repudiation is one of the five pillars of information assurance, which is the practice of managing information-related risks and protecting information systems, like computers, servers, and enterprise networks. The other four pillars are confidentiality, integrity, availability, and accountability. Non-repudiation is essential in digital contracts and email, where a signatory of an email on one side of communication cannot deny sending the message, and the receiver cannot deny receiving it.

In summary, non-repudiation is a service that provides proof of the origin and integrity of data, ensuring that no party can deny sending or receiving a communication using encryption and digital signatures. It is a crucial aspect of information assurance and cybersecurity, and it helps to prevent message forging and disputes over the legitimacy of data transfers.