css-cryptosystem

The Content Scramble System (CSS) is a cryptosystem that utilizes plaintext, a key of 30 bits, two Linear Feedback Shift Registers (LFSR) of sizes 17 and 25, and Full Adder. This cryptosystem is unique because the actual bits that compose the plaintext characters and key are utilized. One of the most interesting features of this cryptosystem is that the LFSRs don’t utilize the actual plaintext characters at all. Instead, the supplied key and length of the plaintext are iterated over to generate deterministic bits of ‘0’ or ‘1’. The plaintext isn’t utilized until the Full Adder step, where the appropriate ‘0’ or ‘1’ is added to the current bit and modded by 2. The process then repeats itself in reverse with no actual modifications to the ciphertext.

Dependencies

The only requirement for this implementation is base Python 3.

Usage

If necessary, edit the plaintext and keyword variables in main.py. Most characters, including punctuation, are acceptable. The key must be exactly 30 bits or 5 characters. When finished, run:

$ python /path/to/css.py

Example

 shanekimble@Shanes-MacBook-Pro  ~  python Documents/Code/Git_summonholmes/css-cryptosystem/css.py 
The keyword:  Shane
The plaintext:  OnemansmagicisanothermansengineeringSupernaturalisanullwordOnemanstheologyi
The ciphertext:  xh`/|\F/rq?O#Wۏ`-OО@*cV
                                         |iSˈ)j    `;/
                                                   3r\͸o;T+CNDt7tGLۨ`}B
The dectext:  OnemansmagicisanothermansengineeringSupernaturalisanullwordOnemanstheologyi

License

This project is licensed under the GNU General Public License GPLv3.