Digital signatures primarily provide non-repudiation and authenticity.

• A. Confidentiality
• B. Data compression
• C. Random number generation
• D. Non-repudiation and authenticity

Answer: (D)

Digital signatures are used to prove who authored a message and to prevent denial of authorship. Authenticity is achieved because the signature is created with the signer’s private key and can be verified with the signer’s public key; if verification succeeds, it shows the message originated from the holder of that private key and hasn’t been altered since signing. Non-repudiation follows from that same link: once something is signed with the signer’s private key, the signer cannot credibly claim they didn’t sign it, assuming the private key remains secure. Confidentiality, on the other hand, concerns keeping content secret, which signatures do not address. Data compression is unrelated, and while some signature schemes use randomness internally, that isn’t the purpose of signing itself.