Which term is used to describe a mechanism that prevents a sender from later denying sending a message?

Which term is used to describe a mechanism that prevents a sender from later denying sending a message?

• A. Authentication
• B. Confidentiality
• C. Nonrepudiation
• D. Integrity

Answer: (C)

Nonrepudiation is the assurance that a sender cannot later deny having sent a message. It’s achieved by binding the sender’s identity to the message through mechanisms like digital signatures, timestamps, and auditable logs. In practice, a digital signature is the common way to realize nonrepudiation: the sender signs the message with their private key, and anyone with the corresponding public key can verify the signature and the message’s content. Because producing a valid signature requires the private key, which only the true sender should possess, the sender cannot plausibly deny authorship later. This idea is distinct from authentication, which is about confirming who is at the other end of a communication; confidentiality keeps the message secret from unauthorized parties; and integrity ensures the message hasn’t been altered, but by itself it doesn’t prove who sent it or prevent denial of sending. Nonrepudiation adds that verifiable tie between the sender and the message, often supported by trusted certificates, secure key management, and proper logging.

Nonrepudiation is the assurance that a sender cannot later deny having sent a message. It’s achieved by binding the sender’s identity to the message through mechanisms like digital signatures, timestamps, and auditable logs.

In practice, a digital signature is the common way to realize nonrepudiation: the sender signs the message with their private key, and anyone with the corresponding public key can verify the signature and the message’s content. Because producing a valid signature requires the private key, which only the true sender should possess, the sender cannot plausibly deny authorship later.

This idea is distinct from authentication, which is about confirming who is at the other end of a communication; confidentiality keeps the message secret from unauthorized parties; and integrity ensures the message hasn’t been altered, but by itself it doesn’t prove who sent it or prevent denial of sending. Nonrepudiation adds that verifiable tie between the sender and the message, often supported by trusted certificates, secure key management, and proper logging.