What encryption type is primarily used for digital signatures and key management?

• A. Symmetric encryption
• B. Hash function encryption
• C. Public-key encryption
• D. Block cipher encryption

Answer: (C)

Public-key encryption is the correct choice because it utilizes a pair of keys—a public key and a private key—to facilitate secure communication and ensure the integrity and authenticity of messages. This method is essential for digital signatures, which are used to verify the identity of the sender and ascertain that the message has not been altered in transit. The sender signs the message using their private key, and the recipient can verify the signature with the sender's public key.

Additionally, public-key encryption is important for key management because it allows secure exchange of symmetric keys used for session encryption. In this scenario, the symmetric key can be encrypted with the recipient's public key and sent to them securely.

Other encryption types like symmetric encryption involve the use of a single key for both encryption and decryption, which is not ideal for scenarios that require secure authentication or signatures. Hash function encryption, on the other hand, is primarily used for data integrity and does not involve reversibility, meaning it does not serve as a method for encryption in the traditional sense. Finally, block cipher encryption refers to a specific method of symmetric encryption that divides data into blocks and encrypts them but lacks the distinct advantages of key management and digital signatures provided by public-key systems.