Monoalphabetic Cipher

cryptography

Definition

Monoalphabetic Cipher

A monoalphabetic cipher is a substitution cipher in which each plaintext symbol is replaced by a fixed symbol in the ciphertext according to a key that defines the mapping.

Security

Vulnerability to Statistical Analysis

The brute-force key space is $26!\approx 4.032\times 10^{26}$ for the Latin alphabet, but a monoalphabetic substitution does not hide the frequency distribution of letters in the plaintext. An attacker can recover the plaintext by matching symbol frequencies to those of the natural language.