Which term describes cryptography using two keys where one encrypts and the other decrypts?

• A. Symmetric
• B. Encoding
• C. Hash Function
• D. Asymmetric

Answer: (D)

Two-key cryptography, where one key encrypts and the other decrypts, is asymmetric cryptography. It relies on a key pair—a public key that can be shared openly and a private key that remains secret. Messages encrypted with the public key can only be decrypted with the corresponding private key, and signatures created with the private key can be verified with the public key. This separation of keys is what distinguishes it from symmetric systems, which use the same key for both encryption and decryption. Encoding simply changes data format and is not about protecting confidentiality, and a hash function is a one-way function used for integrity, not for reversible encryption.