Non-repudiation is typically achieved through which mechanism?

• A. Regular backups.
• B. Two-factor authentication.
• C. Digital signatures and audit trails.
• D. Data erasure.

Answer: (C)

Non-repudiation means that once a person takes an action or signs a message, they cannot credibly deny it later. The strongest way to achieve this is through digital signatures and audit trails. A digital signature uses a private key to sign data, and anyone with the corresponding public key can verify that the signer created the signature and that the data hasn’t been altered. This creates a verifiable link between the signer and the specific message, making denial highly improbable. Audit trails capture who did what and when, and when these logs are protected against tampering (often with cryptographic safeguards and secure storage), they provide an authoritative record of actions for later verification. Together, they provide proof of origin, integrity, and sequence of events—key ingredients for non-repudiation. Regular backups protect data availability, two-factor authentication strengthens identity verification at access time, and data erasure focuses on removing data; none of these by themselves establish that a specific person performed a particular action or signed a specific item.