Which cipher uses alphabetic substitution with multiple alphabets?

• A. Substitution Cipher
• B. Polyalphabetic Cipher
• C. Caesar Cipher
• D. Transposition Cipher

Answer: (B)

Polyalphabetic ciphers perform alphabetic substitution using several alphabets. In a monoalphabetic substitution, each letter maps to a single ciphertext letter with one fixed alphabet, so letter frequencies stay recognizable. A polyalphabetic system, however, switches which alphabet is used for each position in the message, often guided by a key, so the same plaintext letter can encrypt to different ciphertext letters depending on where it appears. This makes patterns harder to detect with frequency analysis. A classic example is the Vigenère-style approach, which uses a sequence of shifted alphabets determined by the key. The other types described either use a single alphabet for substitution (like a Caesar shift) or do not substitute letters at all but rearrange their positions (transposition). Hence, alphabetic substitution with multiple alphabets points to a polyalphabetic cipher.