Cryptos-App - Project Documentation

1. Overview

Cryptos-App is a cross-platform desktop application combining a Flutter-based GUI with Python backend logic for cryptographic operations. The app enables users to encrypt/decrypt data using classical and modern algorithms, with seamless communication between the Flutter interface and Python scripts via the Process class.

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2. Features

Supported Cryptographic Methods

Classical Cryptography

1. Substitution Ciphers
   • Vigenère Cipher
   • Playfair Cipher
2. Transposition Ciphers
   • Columnar Transposition

Modern Cryptography

1. Symmetric Key Algorithms
   • AES (Advanced Encryption Standard)
2. Asymmetric Key Algorithms
   • RSA (Key generation, encryption/decryption)
3. Hashing
   • SHA-256, MD5
4. Diffie-Hellman Algorithm

Core Functionalities

• Algorithm selection via Flutter dropdown menu.
• Text encryption/decryption with real-time results.
• Key input fields (where applicable).
• Error handling for invalid inputs.

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3. Technical Specifications

Architecture

• Frontend: Flutter (Desktop compatible) for GUI.
• Backend: Python scripts for cryptographic logic.
• Communication: Flutter Process class to execute Python scripts with arguments.

Dependencies

• Python:
  • sys (for command-line argument parsing).
• Flutter:
  • process_run package for process management.

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4. Python Backend Structure

File Organization

• scripts/
  • vigenere.py
  • playfair.py
  • aes.py
  • rsa.py
  • hashing.py
  • ...

Function Requirements

All Python scripts MUST adhere to the following input/output conventions:

Input Format

• Accept arguments via command line using sys.
• Required arguments:
  • encode, decode, or hash.
  • plaintext/ciphertext.
  • if applicable, e.g., AES key or Vigenère keyword.

Output Format

• Return results as a Plain text string to stdout.
• Example for encryption with a <key>:

  <encrypted_text>  
  
  

Example Python code:

import sys  

def aes_encrypt(plaintext, key):  
    # Implementation logic here  
    return ciphertext  

if __name__ == "__main__":
    if len(sys.argv) != 4:
        print("Usage: python aes128.py [encode|decode] [text] [key]", file=sys.stderr)
        sys.exit(1)

    operation = sys.argv[1].lower()
    text = sys.argv[2]
    key = sys.argv[3]

    if operation == "encode":
        print(aes_encrypt_string(text, key))
    elif operation == "decode":
        print(aes_decrypt_string(text, key))
    else:
        print("Invalid operation. Use 'encode' or 'decode'.", file=sys.stderr)
        sys.exit(1)  

7. Conclusion

This hybrid architecture leverages Flutter's rich UI capabilities and Python's robust cryptographic libraries, providing a flexible and scalable solution. By standardizing input/output formats and using process-based communication, the system ensures maintainability and ease of extension for new algorithms.