What is the difference between symmetric and asymmetric encryption?

• A. Symmetric uses one key for encryption and decryption; asymmetric uses a public/private key pair.
• B. Symmetric is slower and uses key pairs; asymmetric uses a single shared key.
• C. Symmetric uses a public key; asymmetric uses a private key only.
• D. Symmetric encryption is not used in TLS.

Answer: (A)

The main idea here is how keys are used in symmetric vs. asymmetric encryption and what that means for performance and security. Symmetric encryption uses the same key to both encrypt and decrypt data. That makes it very fast and suitable for encrypting large amounts of data, but the challenge is safely sharing that secret key with the recipient so it isn’t intercepted.

Asymmetric encryption, on the other hand, uses a pair of keys: a public key that can be shared openly to encrypt, and a private key that only the owner can use to decrypt. This setup eliminates the need to distribute a secret key in advance and enables things like digital signatures and secure key exchange.

In real-world protocols like TLS, the handshake usually leverages asymmetric cryptography to establish trust and securely exchange a session key, and then that session key is used with symmetric encryption to protect the actual data because it’s much faster.

So the statement correctly captures the essential difference: symmetric uses one key for encryption and decryption, while asymmetric uses a public/private key pair. The other options misstate speed and key usage, or TLS integration.