Which option describes the correct characteristic of symmetric (shared key) encryption?

• A. Symmetric encryption uses two keys, while asymmetric uses one.
• B. Symmetric encryption uses a single shared key, while asymmetric uses a public/private key pair.
• C. Symmetric encryption is always slower than asymmetric encryption.
• D. Symmetric encryption does not require any key exchange.

Answer: (B)

Symmetric encryption is defined by using a single shared key for both encryption and decryption. Both parties must have the same secret key in advance, which is why securely distributing that key is a central practical concern. This equality of keys is what makes the approach fast and suitable for bulk data, but it also means a secure key exchange mechanism is essential.

The correct description captures this idea: symmetric encryption uses one shared key, while asymmetric encryption uses a public/private key pair. The other statements mix up how keys are used or performance: symmetric isn’t defined by using two keys, and it isn’t inherently slower than asymmetric (in fact, it’s generally faster). It also does require some form of key exchange to share the secret key securely.