Some lua tools for vigenere encryption, decryption and brute-force.
Based on the basic Blaise de Vigenère algorithm.
Vigenère cipher is a enhancement of Caesar's cipher. This is a substitution encryption technique as plain text letters are replaced by some fixed number of positions down the alphabet.
To implement it we need a plain-text and a key. Assuming the text is Vigenere and the key is lua . We map every alphabet character to its position :
a = 0, b = 1, c = 2, [...] z = 25
and we repeatedly add the key values to our plain text :
VIGENERE
LUALUALU
||||||||
GCGPHECY
Encoded text is GCGPHECY.
Required libraries :
- lua (tested on 5.1.5)
Clone the repository
git clone https://github.com/raymas/Vigenere.git
Four functions are implemented : three for a ciphertext-only attack, one for encryption.
You have three operation mode for this script :
- e for encryption
- d for decryption
- c for cracking
lua vigenere.lua [e|d|c]
Each modes have their specific arguments
Encryption 'e'
Options
--raw [text on cli]
--file [path to file]The last argument should always be the key!
Usage : lua vigenere e --file plaintext.txt mysecretkey
Decryption 'd'
Options
--raw [text on cli]
--file [path to file]The last argument should always be the key!
Usage : lua vigenere d --file ciphertext.txt mysecretkey
Crack 'c'
Options required either one or the other.
--raw [text on cli]
--file [path to file]Options optional either one or the other.
--maxkeylength [integer of maximum key length by default it is 20]
--trylength [minimum length:maximum length]The --maxkeylength argument try to guess the key with a maximum number of characters.
--trylength [lower:upper] output a key guesses from lower to upper bounds.
Usage example :
lua vigenere c --file ciphertext.txt --maxkeylength 12
lua vigenere c --file ciphertext.txt --trylength [1:20]Brute force
keylengthguess(text, language, maxkeylength, verbose)
guessingKey(text, language, keylength, verbose)
decrypt(text, key, language)You can use the three function to try a brute force decryption.
Firstly, we have to guess the key length using a frequency analysis of every letter in the encrypted text. It works better with long text as the key is repeating multiple times.
Secondly, we have to guess the key based on block chain and a frequency analysis for each character of the key.
Thirdly, we try a decryption with key that we just guess.
Please read CONTRIBUTING.md for details on our code of conduct, and the process for submitting pull requests to us.
- raymas - Initial work - raymas
See also the list of contributors who participated in this project.
This project is licensed under the GNU 3.0 License - see the LICENSE.md file for details