Lightweight Cryptography Algorithm ~ LightCrypt (LCA-128)

LightCrypt is a custom 128-bit encryption algorithm I built from scratch as my first project in learning cryptography. It's specifically designed for small, low-power devices like IoT sensors, smart home gadgets, and embedded systems that need to encrypt data but have limited processing power and battery life.

Why LightCrypt?

Traditional encryption algorithms like AES can be too heavy for tiny devices. LightCrypt solves this by being:

1. Lightweight: Uses minimal memory and processing power
2. Fast: Optimized for quick encryption/decryption
3. Secure: Still provides strong data protection

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How It Works

LightCrypt uses a Substitution-Permutation Network (SPN) - a proven cryptographic structure that:

1. Substitutes data using lookup tables (adds confusion)
2. Permutes bits around (spreads changes across the data)
3. Repeats this process 10 times with different keys

Technical Specs

• Block Size: 128 bits (16 bytes at a time)
• Key Size: 128-bit encryption key
• Rounds: 10 cycles of substitution and permutation
• Structure: Substitution-Permutation Network (SPN)

Perfect for: IoT sensors, Arduino projects, battery-powered devices, and learning cryptography fundamentals.

LightCrypt Architecture:

Plaintext (128 bits) → AddRoundKey → [SubBytes → ShiftRows → AddRoundKey] × 10 rounds → Ciphertext

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Key Concepts:

1. Confusion: Makes relationship between key and ciphertext complex (S-box)
2. Diffusion: Spreads influence of single plaintext bit across many ciphertext bits (permutation)
3. Key Schedule: Generates round keys from master key
4. Rounds: Multiple iterations increase security

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Project Structure

│── src/ │ └── lightcrypt.py # Core cipher implementation │── demo/ │ └── demo.py # Example encryption/decryption usage │── test/ │ └── test_lightcrypt.py # Unit tests (pytest) │── benchmark/ │ ├── standard_benchmark.py # Benchmark LightCrypt only │ └── compare_benchmark.py # Compare LightCrypt vs AES |── encrypt.py |── decrypt.py │── README.md

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Installation

Clone the repository and install dependencies:

git clone https://github.com/DivInstance/lightweight-cryptographic-algorithm
cd lightweight-cryptography-algorithm
pip install -r requirements.txt

Dependencies:

1. Python 3.11+
2. pytest for testing
3. pycryptodome for AES benchmark

Usage

Run Encryption/Decryption

From the project root directory:

Encrypt and Decrypt message

python -m encrypt  

python -m decrypt 

Lightcrypt Module

python -m src.lightcrypt

Alter the message value to encrypt/decrypt in the main function your own message.

Demo Script

Run the demo to see example encryption/decryption on IoT-style payloads:

python -m src.demo

Run Tests

Unit tests (pytest):

pytest -v

Benchmarking

Benchmark LightCrypt vs AES-128:

python -m benchmark.compare_benchmark

Results (500 iterations, ECB mode)

LightCrypt (LCA-128):

Encryption: 4.1924 sec (119.26 KB/s) Decryption: 4.2446 sec (117.80 KB/s)

AES-128 (ECB):

Encryption: 0.0034 sec (146838.82 KB/s) Decryption: 0.0030 sec (165573.35 KB/s)

Future Enhancements for LightCrypt

• Raspberry Pi Optimization & IoT Testing : Test LightCrypt on actual Raspberry Pi hardware to measure real-world IoT benchmarks.
• Statistical Security Analysis & Randomness Testing: Perform NIST tests and avalanche analysis to validate cryptographic security.
• CBC Mode Implementation & Hardware Translation: Add CBC mode and create a C version for microcontroller/Arduino deployment.

Acknowledgements / Credits

This is my first project in cryptography. I built LightCrypt (LCA-128) to learn and understand the principles of block ciphers and secure coding.

References and resources that helped in designing the Substitution–Permutation Network (SPN) structure:

• Cryptography textbooks and online resources on SPN ciphers
• Research papers on lightweight block ciphers for IoT and embedded systems
• Practical examples of AES and other standard block ciphers

License

This project is licensed under the MIT License – free to use, modify, and distribute.

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