// # Project 1: DES - based Feistel Cipher Implementation
Team Member: Yuhan Wan & Ying Zhou Date: March/20th/2025

Task Assignment:

• CharToBin: YW
• Cipher:
  • encryption: YW
  • decryption: Ying
• FeistelFunctions: YW
• KeySchedule: YW && Ying
• Main: YW && Ying
• Permutation: Ying
• ReadFile: Ying
• SBox: YW

This project implements a basic file encryption and decryption system using a simplified Feistel network. The program reads a plaintext file, encrypts or decrypts the contents using a user-provided 7-character password, and compute the test cases output to a specified file.

Features:

• Feistel-based Cipher:
• 10 rounds of Feistel encryption
• 32-bit subkeys used in each round
• Includes S-Boxes and P-Box permutation
• Customizable File I/O:
• User-specified input and output file names
• Encryption and decryption options via command line
• Password Handling:
• User enters a 7-character password
• Password is automatically converted into binary for use as the encryption key
• Bit-level Processing:
• Input file is processed as binary
• Encryption is performed bit-by-bit
• Binary File Output:
• Encrypted file can be safely stored and later decrypted