Which term is described as the process of converting ciphertext back into plaintext?

• A. Decryption
• B. Cipher
• C. Kerckhoffs's Principle
• D. Encryption

Answer: (D)

Decryption is the process of converting ciphertext back into plaintext. When information is encrypted, plaintext becomes ciphertext to protect its confidentiality. Decryption reverses that operation, using the appropriate decryption algorithm and key to recover the original message. In symmetric systems, the same secret key is used to encrypt and decrypt; in asymmetric systems, the recipient uses a private key to decrypt data that was encrypted with a public key. The term for turning plaintext into ciphertext is encryption, which is the opposite action. A cipher is the method or algorithm that enables encryption and decryption, and Kerckhoffs's Principle is about the security of a cryptosystem even when the algorithm is public—it’s not the process of reversing ciphertext.