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

~$ time

Script & Source	Time Taken
Brutes Each Char (example Dir)	60 Minutes
Vigenère Cipher Decoder (This)	0.484 Seconds

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

~$ cat usage.txt:

• 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)

   _    _ _
  | |  | (_)
  | |  | |_  ____  ____ ____   ____  ____ ____
   \ \/ /| |/ _  |/ _  )  _ \ / _  )/ ___) _  )
    \  / | ( ( | ( (/ /| | | ( (/ /| |  ( (/ /
     \/  |_|\_|| |\____)_| |_|\____)_|   \____)
           (_____|                @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

~ $ cat faq.txt

• 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...

~$ ./social: