Which of the following is an example of asymmetric encryption?

• A. AES
• B. Blowfish
• C. 3DES
• D. RSA

Answer: (D)

Asymmetric encryption uses a pair of keys: a public key for encryption and a private key for decryption. This allows secure communication without sharing a secret key in advance. RSA is a classic example of this approach, based on the difficulty of factoring large numbers; one key can be used to encrypt, and only the corresponding other key can decrypt it. Symmetric encryption, on the other hand, uses the same key for both encryption and decryption, which is why algorithms like AES, Blowfish, and 3DES are categorized as symmetric ciphers. They’re fast and suitable for protecting large amounts of data, but require a secure way to distribute the secret key beforehand. In practice, systems often use asymmetric methods to securely exchange a symmetric key, then use that symmetric key to encrypt the actual data for efficiency.