What term refers to the original readable data before any encryption is applied?

• A. Cipher
• B. Ciphertext
• C. Kerckhoffs's Principle
• D. Plaintext

Answer: (D)

Plaintext is the original readable data before encryption. It’s the raw information you start with, which the encryption process uses as input. After applying the chosen algorithm (the cipher) and a key, that plaintext becomes ciphertext—the scrambled data that isn’t understandable without the key. When you decrypt, you return to the original plaintext. The other terms have different roles: a cipher is the method used to transform data, ciphertext is the encrypted output, and Kerckhoffs’s Principle is about designing systems so security doesn’t rely on keeping the algorithm secret.