TLDR: Non-repudiation is a security principle ensuring that the sender of a message or the signer of a document cannot deny their actions. It provides irrefutable proof of the origin, integrity, and receipt of data or communications. Achieved through technologies like digital signatures and public key infrastructure (PKI), non-repudiation is essential in secure communications, legal transactions, and digital agreements.
https://en.wikipedia.org/wiki/Non-repudiation
Non-repudiation relies on cryptographic mechanisms to verify the authenticity of a user or entity. A digital signature is a common tool for enforcing this principle, as it binds the signer to the signed document using their private key. This ensures that only the intended signer could have created the signature. For example, in e-commerce, non-repudiation protects against a buyer denying a purchase or a seller denying the issuance of an invoice, fostering trust in online transactions.
https://www.nist.gov/itl/special-publications/nist-special-publication-800-107
Applications of non-repudiation extend to secure email communication, software distribution, and blockchain-based systems. In legal contexts, it is critical for verifying the authenticity of contracts and agreements, ensuring that parties cannot dispute their involvement. By combining digital signatures with timestamping and audit trails, non-repudiation ensures accountability and transparency in digital ecosystems, making it a cornerstone of modern security practices.