Non-repudiation is a core security principle that ensures an individual or system cannot deny having performed a specific action. In cybersecurity, this concept is critical for accountability, auditing, and legal enforcement. Non-repudiation provides assurance that an action—such as sending an email, approving a transaction, or signing a document—can be definitively attributed to a specific user.

This principle is commonly enforced using cryptographic techniques such as digital signatures, public key infrastructure (PKI), hashing, and secure logging. For example, when a user digitally signs a document using their private key, anyone can later verify that signature using the corresponding public key. This prevents the signer from denying authorship.

Non-repudiation is particularly important in financial systems, legal documents, and regulated environments where proof of action is required. It differs from authentication, which verifies identity, and authorization, which defines permissions. Non-repudiation focuses on ensuring that actions are traceable and undeniable, supporting forensic investigations and compliance with security and legal requirements.