A ________ is a mathematical process used in encryption and decryption.

• A. Key
• B. Cipher
• C. Plaintext
• D. Coding Method

Answer: (B)

The mathematical procedure used in encryption and decryption is a cipher. It’s the algorithm that defines how to transform readable data into unreadable ciphertext and then reverse that process to recover the original message. The key is separate data used by the cipher to control the transformation; without the key, the process cannot be reversed correctly. Plaintext is the original, readable message before encryption, not the method itself. A coding method is a broader term and isn’t specific to the algorithmic transformation that secures the data. So the cipher best fits as the actual mathematical process performing encryption and decryption.