Version 3.0 - 15/4/2021
Mealy is a small tool used to cipher and decipher a text file using a Mealy machine. Ciphered messages can be hidden in an image using steganography..
This Python tool can be used in batch mode with parameters or with a (GUI) Graphical User Interface based on Tkinter if user doesn't give any parameter.
Author : Thierry Maillard
- Python 3.6+ must be installed on your computer. To check, open a Terminal Window and type in python3 -V. Download the latest Python version on web site : https://www.python.org/downloads
- Mealy project folder : https://github.com/Thierry46/mealy
- To use steganographic features, download and install following python module with pip3 tool : Module Image Python Imaging Library (Pillow) : https://python-pillow.org, maintained by Alex Clark (PIL Fork Author). Command to install or upgrade : python3 -m pip install --upgrade Pillow
- Module stepic version 0.5.0 : https://launchpad.net/stepic : licence GNU GPL 2 maintained by Scott Kitterman and Lenny Domnitser. Command to install or upgrade : python3 -m pip install --upgrade stepic
- On Windows, double-click on run_Mealy.py
- Launch run_Mealy.py in a terminal : go to src directory and launch with command python3 run_Mealy.py
- On Mac, associate src/run_Mealy.py with Python Launcher : In finder select src/run_Mealy.py, right single click, Open with : Python Launcher App (3.9.1) (If not proposed, Python Launcher is located in /Applications/Python 3.9)
- Enter your secret keys and then click Go Next ... button.
- Tell the program your secret message and then click Go Next ...
- The ciphered text is displayed
- Save the result in a file or hide it in an image.
- Enter your secret keys you received and then click Go Next ... button.
- In the cyphering window : Click on the Decipher radio button, Insert in the orange text editor the content of the ciphered file you received by clicking Insert from a file... button and then click Go Next ...
- The deciphered message appears
- Save the result in a file or copy it in the clipboard.
This estimation is done according the algorithm described in the Programmer's guide. Breaking the machine consist in discovering secret keys.
Knowing a message and its ciphered version :
If only one numeric key is used in the range [0; 9223372036854775807] to cypher the message and if the message is long enough, the maximum of attempt is around 5e18 at the condition user gives a long enough numeric key ! If a second key of length 50 characters is used to modify alphabet order, the last number of attempt should be multiply by the maximum number of cyclic possible permutation of the alphabet (100 characters) : 100! / ((100-50)!*50).
See programmer's guide.
Copyright 2021 Thierry Maillard This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses.