AES-128 Inverse Key Expansion & Forensic Analysis Tool

A Java-based cryptographic utility that reverses the AES-128 round key generation process to reconstruct the original 128-bit encryption key and all previously generated round keys. Designed for cryptographic research, forensic analysis, debugging, and educational purposes.

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📑 Table of Contents

• 📖 Overview
• ✨ Features
• 🚀 Getting Started
• ⚡ Usage
• 📘 How It Works
• 🛠️ Project Structure
• 🗺️ Roadmap
• 🤝 Contributing
• 📜 License

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📖 Overview

AES-128 uses a key schedule to generate a series of round keys from the original 128-bit key. This tool performs the inverse key expansion process, allowing users to:

• Reconstruct the original AES-128 key from the final round key.
• Retrieve all 10 round keys used in AES-128 encryption.
• Analyze AES key scheduling for research and educational purposes.

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✨ Features

• Inverse Key Expansion – Reverses the AES-128 key schedule.
• Custom RoundKey Object – Stores round number and corresponding byte array for clean organization.
• Forensic & Educational Applications – Supports learning, validating, and investigating cryptographic systems.

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🚀 Getting Started

Prerequisites

• Java JDK 8+
• Basic knowledge of AES key scheduling (recommended)

Installation

git clone https://github.com/tmfontan/AESRoundKeyInverter.git
cd AESRoundKeyInverter

Compilation

javac RoundKey.java InverseKeyGeneration.java

Execution

java InverseKeyGeneration

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⚡ Usage

The tool prompts for input key data or round keys, then reconstructs:

• The original AES-128 encryption key
• All 10 round keys used in the AES-128 encryption process

Example Output:

Original Key:  2b7e151628aed2a6abf7158809cf4f3c
Round Key 1:   a0fafe1788542cb123a339392a6c7605
Round Key 2:   f2c295f27a96b9435935807a7359f67f
...
Round Key 10:  d014f9a8c9ee2589e13f0cc8b6630ca6

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📘 How It Works

AES-128 performs key expansion to derive round keys:

Key Expansion (Forward):

Original Key --> Round Key 1 --> Round Key 2 --> ... --> Round Key 10

Inverse Expansion (This Tool):

Round Key 10 --> Round Key 9 --> ... --> Original Key

Diagram:

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🛠️ Project Structure

• RoundKey.java – Defines the data structure for holding round numbers and their byte arrays.
• InverseKeyGeneration.java – Contains the logic for reversing AES-128 key scheduling and retrieving the original key.

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🗺️ Roadmap

Planned enhancements and future improvements:

• Add support for AES-192 and AES-256 key inversion.
• Implement a GUI version for easier visualization.
• Provide unit tests for improved reliability.
• Add export functionality to save reconstructed keys.
• Include performance benchmarks.

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🤝 Contributing

Contributions are welcome! To get started:

1. Fork the repository.
2. Create a new branch: git checkout -b feature-name.
3. Make your changes and commit: git commit -m "Add feature".
4. Push to your branch: git push origin feature-name.
5. Submit a pull request.

Please ensure your contributions align with the project’s coding standards and include updates to documentation if necessary.

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📜 License

This project is licensed under the MIT License.

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⚠️ Disclaimer

This project is intended solely for educational and authorized security testing purposes. Do not use it for unauthorized access, decryption, or illegal activities.