What is non-repudiation, and how can a TA help ensure it in communications?

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Non-repudiation means that a party cannot deny having performed a transaction or sending a message. To make that denial impossible, you attach verifiable proof to the action. Digital signatures do this by using the signer’s private key to sign the data; anyone with the signer’s public key can confirm who signed it and that the data hasn’t been altered. Audit trails capture who did what and when, and tamper-evident logs prevent those records from being secretly changed, preserving the integrity of the proof. Time-stamping can add exact timing to the evidence, strengthening its reliability.

A trusted agent helps make this trustworthy in communications by securely managing keys and certificates, enabling proper signing, and maintaining the signed records and logs in a tamper-resistant way. With the TA handling identity assurance, key custody, and secure logging, there’s a verifiable trail that can be produced in disputes or audits, cementing non-repudiation.

Confidentiality is about keeping information secret, which is not the same as non-repudiation; availability is about systems being reachable; data integrity in transit concerns detecting changes to data, not proving who performed an action. Non-repudiation centers on proving who did what and when, which is captured by signatures and reliable logs.