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Enigma Index of Coincidence (IoC) attack

C++ implementation of ciphertext-only attack (IoC) on Enigma

The attack is presented in the following paper: Ciphertext-only cryptanalysis of Enigma by James J. Gillogly

Installation

Clone repository

git clone https://github.com/SamNzo/enigma-IoC-attack.git

Init & update enigma submodule

cd enigma-IoC-attack/enigma
git submodule init
git submodule update

Build executable

cd enigma-IoC-attack
chmod +x make.sh
./make.sh

The executable is then in the build directory

Usage

The attack has three phases:

• the first one determines the most likely rotor order
• the second determines the most likely ring settings & starting positions
• the last one determines the plugboard connections

1. Rotor order

The simplest way to use it is:

./ioc-attack --ciphertext <path to ciphertext file>

You can choose a custom number of rotors to test between 3 and 8.

./ioc-attack --rotors 3 --ciphertext <path to ciphertext file>

For more informations: ./ioc -h rotors

You can also choose a specific reflector

./ioc-attack --reflector C --ciphertext <path to ciphertext file>

For more informations: ./ioc -h reflector

The default configuration tests 5 rotors (namely rotors I, II, III, IV and V) and reflector B

Example

To test 8 rotors with reflector C:

./ioc-attack --rotors 8 --reflector C --message <path to ciphertext file>

The top 10 rotor configurations are displayed as output

2. Ring setting

3. Plugboard

https://www.youtube.com/watch?v=V4V2bpZlqx8

https://en.wikipedia.org/wiki/Bombe

Attack description

If you are interested in the history of the enigma cryptanalysis, read the following book:

Solving the Enigma - History of the Cryptanalytic Bombe by Jennifer Wilcox

Credits

The progress bar was made by https://github.com/gipert/progressbar