Which is a primary use case for asymmetric cryptography?

• A. Bulk data encryption for performance
• B. Verifying message integrity with a shared secret
• C. Generating random numbers
• D. Key exchange and digital signatures

Answer: (D)

Asymmetric cryptography revolves around public/private key pairs, enabling operations that don’t require sharing a secret key in advance. The primary strengths are establishing trust and securing communication: you can negotiate a shared secret over an insecure channel (key exchange) and you can sign messages to prove who sent them and to ensure they haven’t been altered (digital signatures). This combination—key exchange and digital signatures—captures the main use cases of public-key systems, making it the best-fit answer.

Bulk data encryption for performance isn’t done with asymmetric keys alone because those algorithms are computationally heavier; in practice, asymmetric crypto is used to bootstrap a session and then symmetric encryption handles the large volume of data. Verifying integrity with a shared secret points to symmetric MACs, not public-key signatures. Generating random numbers is a general requirement in many algorithms but isn’t the defining purpose of asymmetric cryptography.