What is nonrepudiation?

• A. The process of encrypting a message with public key
• B. The ability to prevent a sender from denying having sent a message
• C. The method of verifying a message's integrity
• D. The method of compressing data

Answer: (B)

Nonrepudiation means ensuring that once a message is sent, the originator cannot credibly deny having sent it. This is typically achieved by signing the message with a private key, creating a digital signature that anyone can verify with the corresponding public key; the signature binds the signer’s identity to the content, providing evidence of authorship. Strengthening this binding often involves certificates that link a public key to a real identity and secure logs or timestamps that preserve the signing event for future verification. Encrypting a message with a public key relates to keeping content confidential, not proving who sent it. Verifying a message’s integrity ensures the content hasn’t changed, but by itself it doesn’t prove who sent it. Data compression is unrelated to proving authorship.