Substitution, Atbash & Affine
Encrypts and decrypts with monoalphabetic substitution: a full 26-letter custom alphabet, the self-inverse Atbash cipher that reverses the alphabet, and the Affine cipher (E(x) = ax + b mod 26). Shows the substitution mapping and validates that the key is a permutation.
Runs 100% in your browser — keys and data never leave your device.
Read the full guide to this tool
Notes
- Any monoalphabetic substitution — however scrambled the key — preserves letter frequencies, so it falls to frequency analysis on enough ciphertext.
- The Affine cipher requires the multiplier a to be coprime with 26, otherwise the mapping is not reversible.
- Runs 100% in your browser — keys and data never leave your device.
Explore the idea
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