Vigenère Cipher Decoder
Decode / Bruteforce Vigenere cipher text using the Flag Format!!

vigenere.py -c "RymJHS{XQ_MOWF_TTXU_DBHQBIZR?}" -t "CatCTF"

• Simply clone the repository. Only python should be installed in your system.

  $ git clone https://github.com/htr-tech/Vigenere-Decoder
  $ cd Vigenere-Decoder
  $ python vigenere.py

  Ouput (Interactive Menu)

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           (_____|                @htr-tech
  
  Input Cipher Text: RymJHS{XQ_MOWF_TTXU_DBHQBIZR?}
  Known/Flag Format: CatCTF
  
  Possible Key: python
  Possible Flag: CatCTF{IS_THIS_EVEN_POSSIBLE?}
  

• You can also use command line argument to run this script.

  usage: vigenere.py [-h] [-c CIPHER] [-t TEXT]
  
  options:
    -h, --help            show this help message and exit
    -c CIPHER, --cipher CIPHER
                          cipher text
    -t TEXT, --text TEXT  known text / flag format

• What is Vigenère Cipher:

  Vigenère cipher is a polyalphabetic encryption algorithm. It is a method of encrypting alphabetic text using a series of different Caesar ciphers based on the letters of a keyword.

  It is considered a stronger cipher than the Caesar cipher because it uses longer keys that allow the letters to be encrypted in multiple ways, making frequency analysis less effective.

• What does this script do?

  This script allows you to decrypt a Vigenere cipher by providing the known part of the plaintext or flag format. It uses a Decoder class to decode the ciphered text with a given key, and a BruteForcer class to attempt to find the decryption key by comparing the flag format with the decrypted text. More details are commented inside the script.

• More to be added...