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The Enigma machine was the electromechanical cipher device used by Germany in WWII, famously broken by Allied cryptanalysts including Alan Turing's team at Bletchley Park. This simulator models a 3-rotor Enigma I with plugboard, including the rotor stepping mechanism's well-known "double-stepping" quirk.
How it works
Choose your three rotors, ring settings, starting position, and any plugboard letter-swap pairs. Each letter steps the rotors, passes through the plugboard, travels right-to-left through all three rotors, reflects, then travels back left-to-right through the rotors and plugboard again to produce the output letter.
- Enter message.
- Enter left rotor.
- Enter middle rotor.
- Enter right rotor.
- Enter ring settings (3 letters, e.g. AAA).
- Enter starting position (3 letters, e.g. AAA).
- Enter plugboard pairs (optional, e.g. AB CD EF).
- Click Calculate to see your results.
Examples
The defining self-reciprocal property
Encrypting a message with a given rotor/ring/plugboard setup, then running the output back through the identical settings, always reproduces the original message exactly — a direct consequence of the reflector making the signal path symmetric. This is the real Enigma machine's most famous property, and it holds here too.
Who should use it
- Learning how the historical Enigma machine actually worked, step by step.
- Recreating and verifying classic Enigma cipher exercises or puzzles.
Industry applications
- Cryptography and computer science education
- History of computing and WWII cryptography education
Advantages
- Reproduces the historical double-stepping rotor anomaly rather than a simplified stepping rule.
- Verified via the machine's own defining self-reciprocal property, not just "it ran without an error."
Limitations
- Educational simulation only — not a byte-for-byte replica of every historical Enigma variant (e.g. the Naval 4-rotor M4).
Common mistakes to avoid
- Using different rotor, ring, or starting-position settings for "decryption" — Enigma requires identical settings for both directions, since it's the same operation.
- Reusing a letter in more than one plugboard pair — each letter can only be swapped with one other letter at a time.
Best practices
- To verify your settings are consistent, run your own output back through with identical settings and confirm you get the original message back.
- Record your rotor order, ring settings, starting position, and plugboard pairs together — all four are required to reproduce the same result later.
Tips
- Start with no plugboard pairs and default rotor settings to see the basic mechanism, then add plugboard pairs to see how much they change the output.