Python3 algorithm to break Vigenère cypher [2] with a given hash of the plain text based on the Kasiski method [1]
These instructions will get you a copy of the project up and running on your local machine for development and testing purposes.
vigenere.py module accepts several flag inputs.
We implemented several heuristics described by the following optional flags --word-length, --key-length--threshold, --occurrences-threshold. These flags establish thresholds to reduce the search space; receiving default values of 4, 4 and 3 respectively. There may exist several specific input samples where default thresholds are not enough to propose a key since they limit the search space excesively. In such cases, new values for these flags may need to be proposed.
| Short flag | Long flag | Input type | Default value | Description |
|---|---|---|---|---|
| -i | --input | File | Input file | |
| -d | --dictionary | File | Dictionary to be used | |
| --hash | File | Hash to be used for comparison | ||
| -wl | --word-length | int | 4 | Length of words for occurrence count in length guessing (Kasiski) |
| -klt | --key-length-threshold | int | 4 | Number of key length candidates to examine (Kasiski) |
| -ot | --occurrences-threshold | int | 3 | Number of top letters to examine for each column (Kasiski) This value greatly increases execution time inversely proportional |
| -v | --verbose | None | False | Verbose mode |
To use this repo, follow these steps:
-
Clone this repository:
$ git clone https://github.com/MartinSandeCosta/vigenere_cryptanalysis.git -
Run the following command to execute:
$ python3 vigenere.py -i input -d dictionary --hash hashIf something goes wrong try increasing the optional flags
The repo includes a script to run tests automatically
- Run the following command to execute:
$ chmod +x run_tests.sh $ ./run_tests.sh
Feel free to contribute! :)
This project has been developed as part of the MSc. in Computer Science at Universidade da Coruña. The software is accompanied by a technical document which details its development.
See also the list of contributors who participated in this project.
This project is licensed under MIT License
[1] Kasiski, F. W. 1863. Die Geheimschriften und die Dechiffrir-Kunst. Berlin: E. S. Mittler und Sohn
[2] Lyons, J. 2016. pycipher. GitHub repository: https://github.com/jameslyons/pycipher