Explain the difference between symmetric and asymmetric encryption and provide an example of each.

• A. Asymmetric uses one key shared between parties; Symmetric uses a public-private key pair.
• B. Symmetric uses a public/private key pair; Asymmetric uses a shared key.
• C. Symmetric key cryptography cannot be used for digital signatures; Asymmetric can.
• D. Symmetric uses one key (AES); Asymmetric uses a public/private key pair (RSA, ECC).

Answer: (D)

Symmetric encryption uses a single secret key to both encrypt and decrypt data. The same key must be shared securely between parties, which makes this approach fast and efficient for handling large amounts of data, but it also creates a challenge: securely distributing and protecting the key. An example is AES, where the same key is used on both ends to lock and unlock the message.

Asymmetric encryption uses a pair of keys: a public key that can be shared openly and a private key that remains secret. Data encrypted with the public key can only be decrypted with the private key, and digital signatures are created with the private key and verified with the public key. This enables secure key exchange and authentication, though it is generally slower than symmetric methods. Examples include RSA and elliptic-curve cryptography (ECC).

Among the options, the statement that symmetric uses one key (AES) and asymmetric uses a public/private key pair (RSA, ECC) correctly matches how these two types operate. The other choices mix up which type uses a shared key versus a key pair and, in one case, imply a limitation about digital signatures that isn’t accurate in the typical use of these techniques.