Which type of cipher substitutes each symbol with another symbol?

• A. Transposition
• B. Substitution
• C. Code
• D. Hash

Answer: (B)

Substitution ciphers replace every symbol in the plaintext with a different symbol according to a fixed mapping. This means each character is substituted individually, so the structure remains the same but the symbols themselves are changed. A simple example is shifting each letter by one: H becomes I, E becomes F, L becomes M, O becomes P, so HELLO turns into IFMMP.

In contrast, a transposition cipher rearranges the order of the characters without changing the characters themselves, so the symbols don’t get substituted. A code system typically maps words or phrases to codewords, which is not a one-to-one symbol substitution. A hash function produces a fixed-length digest and isn’t used for reversible encryption at all, so it isn’t a cipher in this sense.

So, the description fits substitution, where each symbol is replaced with another symbol.