Select ALL statements supported by the lesson about symmetric-key encryption.

### Why this is right - **A** is true: symmetric encryption uses one shared key for both directions of the operation. - **B** is true: anyone who obtains that secret key may be able to decrypt protected information, so the key must be protected. - **C** is true: the lesson contrasts efficient symmetric methods with the greater computational cost of asymmetric methods. ### The concept Symmetric encryption is useful for protecting files, disks, and communication because it can process data efficiently. Its central difficulty is arranging for both parties to obtain the same secret without exposing it. A secure communication design therefore needs a key-distribution method or another way to establish the shared key. Symmetric encryption does not make that problem disappear. ### The other options - **D. It removes the need to exchange or otherwise share a key.**: This describes neither the key requirement nor the main advantage of symmetric encryption. Sharing or securely establishing the secret is its key-management challenge. ### Terms - **Symmetric-key encryption**: Encryption and decryption that use the same secret key. - **Key distribution**: Getting a cryptographic key to the parties who need it while preventing unauthorized access. ### Remember Symmetric encryption is fast, but both parties must securely obtain the same secret key.