Frequency Analysis Attack Simulator

A 1:1 substitution cipher — Caesar, ROT-N, monoalphabetic substitution — never changes how often each letter appears, only which symbol represents it. Comparing a ciphertext's letter histogram against known English frequencies (chi-squared distance) recovers the key from ciphertext alone, with no brute-force key guessing. This is the classical attack that makes these ciphers unsafe for anything beyond education.