Contents
QUICK FACTS
∙ 5 rotors to choose 3
∙ 26³ start positions
∙ Up to 10 plug pairs
∙ ≈1.58×10²⁰ configs
∙ No letter→itself
∙ 26³ start positions
∙ Up to 10 plug pairs
∙ ≈1.58×10²⁰ configs
∙ No letter→itself
01
Introduction
What is Enigma, and why does it matter?
The Enigma machine was an electro-mechanical cipher device used by Nazi Germany throughout World War II to encrypt military communications. Invented in the 1920s by Arthur Scherbius, it was adopted by the Wehrmacht, Luftwaffe, Kriegsmarine, and SS — becoming the backbone of German secret communications.
Invented
1918 by Arthur Scherbius
In service
1926 – 1945
Configurations
≈ 1.58 × 10²⁰
Broken by
Bletchley Park, 1940
🔑 Why Was It Considered Unbreakable?
Enigma's strength came from its polyalphabetic substitution — every keypress changes the substitution alphabet. Press A twice and get two completely different outputs. The number of possible settings (~158 quintillion) meant brute force was impossible for 1940s technology.
⚡ The Double-Edged Sword
Enigma had a critical flaw built into its reflector design: a letter can never encrypt to itself. This seems minor, but it gave Alan Turing and the Bletchley Park codebreakers the foothold they needed to crack it.
02
Using the Simulator
Step-by-step guide to every control and panel
03
How It Works
The complete electrical signal journey
Every keypress sends an electrical signal through a chain of transformations — 11 distinct stages — before lighting a lamp. No transformation is random: every substitution is deterministic and reversible.
Full Signal Path — All 11 Stages
Keyboard
You press a key. An electrical circuit closes.
Plugboard →
If this letter is in a cable pair, it swaps before entering the rotors.
⚙
Right Rotor →
The right rotor substitutes the letter according to its internal wiring.
⚙
Middle Rotor →
Second rotor applies its own substitution — a completely different mapping.
⚙
Left Rotor →
Third rotor applies its substitution. Now heading into the reflector.
Reflector ↔
Bounces the signal back. NEVER maps a letter to itself.
⚙
← Left Rotor
Return path — rotor wiring traversed in reverse.
⚙
← Middle Rotor
Return path through the middle rotor, also in reverse.
⚙
← Right Rotor
Final return path through the right rotor, in reverse.
← Plugboard
If the output letter is in a cable pair, it swaps again on exit.
Lampboard
A bulb lights up showing the ciphertext letter. Never the same as what you pressed!
Rotor I — Substitution Example
JZ
KN
LT
MO
NW
OY
PH
QX
Example: Input J (position 9) outputs K
Input Q (position 16) outputs H
Input Q (position 16) outputs H
Rotor Stepping Mechanism
LEFT
A
turns @ A
MIDDLE
E
turns @ E
RIGHT
Q
turns @ Q
▸ Double-step anomaly: When middle rotor at E → advances again!
▸ Right rotor steps every keypress
▸ Middle rotor steps when right reaches Q
▸ Left rotor steps only when middle reaches E
04
Machine Internals
Rotors, reflector, plugboard — deep dive
⚙ The Rotors (Walzen)
Each rotor is a disc with 26 electrical contacts, connected by internal wiring that scrambles the alphabet. Five rotors (I–V) existed; operators chose 3 and arranged them in a chosen order.
| Rotor | Wiring (A→Z) | Turnover |
|---|---|---|
| Rotor I | EKMFL GDQVZ NTOWY HXUSP AIBRC J | Q |
| Rotor II | AJDKS IRUXB LHWTM CQGZN PYFVO E | E |
| Rotor III | BDFHJ LCPRT XVZNY EIWGA KMUSQ O | V |
| Rotor IV | ESOVP ZJAYQ UIRHX LNFTG KDCMW B | J |
| Rotor V | VZBRG ITYUP SDNHL XAWMJ QOFEC K | Z |
↔ The Reflector (Umkehrwalze)
Unlike rotors, the reflector does not rotate. It pairs each input to a different output — always in reciprocal pairs. Every letter maps to exactly one other letter, never to itself.
REFLECTOR B (Standard Wehrmacht)
A↔Y, B↔R, C↔U, D↔H, E↔Q, F↔S, G↔L, I↔P, J↔X, K↔N, M↔O, T↔Z, V↔W
🔌 The Plugboard (Steckerbrett)
Up to 10 cables connect pairs of letters, swapping them before and after the rotor path — the single largest contributor to Enigma's complexity.
PLUGBOARD MATH
C(26,2) × C(24,2) × ... × C(8,2) / 10! = 150,738,274,937,250
≈ 150 trillion possible configurations with 10 pairs
05
History & Breaking Enigma
From Polish mathematicians to Bletchley Park
1918
Enigma Invented
Arthur Scherbius patents the Enigma machine.
1926
German Navy Adopts Enigma
The Reichsmarine becomes the first branch to adopt Enigma.
1932
Polish Breakthrough
Marian Rejewski and team crack Enigma mathematically, building the 'Bomba'.
1939
Secrets Passed to Britain
Polish intelligence shares Enigma work with Britain and France.
1940
Turing's Bombe
Alan Turing designs the British Bombe exploiting cribs and the no-self-encryption rule.
1941
Naval Enigma Captured
HMS Bulldog captures U-110 with Enigma machine and keys.
1945
War Ends; Secret Kept
ULTRA remains classified until 1974.
🧠 How the Bombe Worked
Turing's Bombe exploited cribs (known plaintext fragments). Common examples: "WETTER" (weather) at the start of weather reports. Knowing that no ciphertext letter equals the plaintext letter narrowed down rotor settings astronomically.
06
Tips & Tricks
Getting the most from the simulator
🔄
Verify Reciprocal Decryption
Encrypt a word, note output, Reset, then type output. You should get original word back.
👁
Watch the Rotor Drums Step
Type slowly and watch center letters change. Right rotor steps every letter; middle rotor steps less often.
🔌
Try With and Without Plugboard
Type same word with and without plugboard — completely different outputs show its contribution.
📐
Open the Wiring Tab
Type a letter and see the active signal path highlighted through each rotor's substitution table.
⚙
Mix Rotor Order
Try same message with rotors in different orders — completely different ciphertext.
🏛
Try a Historical Message
Load 'Barbarossa' preset. Type 'HEILHITLER' — then reset and type the output. You've just experienced what German operators did daily.