Which statement correctly describes symmetric encryption?

• A. Asymmetric uses public and private keys; best for key exchange.
• B. Symmetric uses the same key for encryption and decryption; suitable for bulk data.
• C. Symmetric is only used for digital signatures.
• D. Asymmetric cannot be used for key exchange.

Answer: (B)

Symmetric encryption uses the same key to both encrypt and decrypt data, which makes the process fast and well-suited for handling large volumes of information (bulk data). Because the same secret key is shared between sender and recipient, it minimizes computational overhead, allowing quick protection of large datasets. The trade-off is securely distributing and managing that secret key; if the key is exposed, confidentiality is lost, so systems often combine symmetric encryption for the data with an asymmetric method to exchange or protect the key.

The idea that symmetric encryption is only for digital signatures is incorrect—digital signatures are a feature of public-key (asymmetric) systems, not the shared-secret approach used for confidentiality. The claim that asymmetric cannot be used for key exchange is also false; public-key protocols like Diffie-Hellman are specifically designed to establish a shared secret over an insecure channel, which is a common way to enable symmetric encryption securely.