About this repository

• A Repository for cryptography homework of S-DES instance, teamed up with Yuyang Hu @Gracivio.

Introduction of S-DES

• S-DES, simple-data encryption standard, is a classic cryptography algorithm, which including mechanics such as S-Boxes, P-Boxes, swapper function and shift function.

Features

In this instance, we created four features to choose from.

1. Generating Keys
   • Secrets module is used in this feature, which generate 10-bits random master key. It's advised to protect the master key to guard the security of the algorithm.(10-bits is easy to crack XD)
2. Encryption
   • Following S-DES process, we encrypt plain text along initial permutation, round function(subkey 1), swap, round function(subkey 2) and reversed initial permutation to get the cipher text. Also, ASCII encoding or binary encoding style are provided. Long text is also transformable.(There may be garbled code in long text transformation)
   • When encrypting the ASCII code in English, each letter will be encrypted in sequence into an 8-bit length binary code, and the result will be converted back to the ASCII code for output.
3. Decryption
   • Following S-DES process, we decrypt plain text along initial permutation, round function(subkey 2), swap, round function(subkey 1) and reversed initial permutation to get the plain text.
   • When it comes to long text, the process of decryption is as the same as the process of encryption except the order key used in the process.
4. Crack
   • Given plain text and corresponding cipher text to crack what master keys may be used. Showing potential keys on the screen and displaying the time to crack out the keys.
   • Crack process information will be displayed in the terminal.
   • ASCII and binary styles are provides, however the garbled code issue cannot fixed, you can only copy the garbled code for some of ASCII crack processes.

GUI

• We use tkinter and ttkbootstrap for user interface. Relative layout is used for best compatibility.(Although some devices may see wrong layout due to screen size)

How to use

• Download the S-DES.py above and run it and you need to download some python packages to meet the environment this application runs on including tkinter and ttkbootstrap
• For the key is presented on screen with password form, which is demonstrated as '*', you should mark your key so that you can use it correctly.

Test results

• Check Test Results.md for the test results, gif is provided for better demonstration

FYI

• Since it's a executable file, there is no interface. Yet functions that intergerned in this file can be used.