In DSAC contexts, what does non-repudiation mean and how can it be achieved?

• A. DAC uses mandatory, system-wide policies to grant access.
• B. Audit logs alone ensure non-repudiation.
• C. Ensuring actions cannot be denied; achieved via digital signatures, audit logs, and robust identity verification.
• D. Non-repudiation is achieved by encrypting all communications.

Answer: (C)

Non-repudiation means you can’t deny having performed a specific action, because there is verifiable evidence linking the action to a real, authenticated identity. In DSAC contexts, this is achieved by combining three elements: digital signatures, audit logs, and strong identity verification. Digital signatures cryptographically bind the content to the signer, allowing anyone with the signer’s public key to confirm who originated it and that the content hasn’t been altered. Audit logs provide a time-stamped, tamper-evident record of what was done, by whom, and when, creating an auditable trail. Robust identity verification ensures the signer is genuinely who they claim to be, reducing impersonation risk and making the signature trustworthy. Together, these pieces form a reliable, non-repudiable record of actions.

Relying on policies alone doesn’t create verifiable proof. Logs by themselves can be tampered with or disputed. Encrypting all communications protects confidentiality but does not prove who performed an action or link it to an identity.