🔒 TwistLock – Custom File Encryption with GUI

TwistLock is an educational file encryption program built in Python.
It features a custom reversible cipher, passphrase-based keying, and both a CLI and Tkinter GUI interface for encrypting and decrypting files.

⚠️ Note: TwistLock is not an industry-grade cipher. It was designed for learning purposes and should not be used to protect sensitive information.

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✨ Features

• Custom encryption algorithm
  • Multi-step reversible transform:
    • Position permutation
    • Byte rotations
    • XOR keystream
    • Half-block swap
    • Substitution (S-box)
  • Passphrase + random salt → SHAKE-256 KDF → unique key material
• File I/O
  • Encrypts/decrypts arbitrary text or binary files
  • Chunked file processing (64 KB per chunk)
  • Simple file header (tag + salt)
  • Error handling for missing files, permission errors, or identical input/output paths
• Cross-platform interfaces
  • CLI mode – text-based menu for fast usage
  • GUI mode – Tkinter-based graphical interface with file pickers, status messages, and passphrase entry
• Bonus functionality
  • Key-based encryption (user supplies passphrase)
  • GUI file selector for extra usability

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🚀 Getting Started

Requirements

• Python 3.6+
• Tkinter (ships with most Python distributions)

Installation

Clone this repository:

git clone https://github.com/YOUR-USERNAME/twistlock.git
cd twistlock