INFO-F514: Visual Cryptography

About The Project

This repository contains the implementation and critical analysis of the Visual Cryptography scheme originally introduced by Moni Naor and Adi Shamir in 1994[cite: 1].

The core idea of this scheme is to share a secret image among $n$ participants in such a way that any $k$ participants can recover the image simply by stacking their printed shares (transparencies) together[cite: 1]. This process requires absolutely no computational power or cryptographic keys for decryption, relying entirely on the human visual system[cite: 1].

This project explores the theoretical foundations of the scheme (information-theoretic security) and evaluates its practical limitations in real-world scenarios, specifically regarding pixel expansion ($m$) and visual contrast ($\alpha$) degradation[cite: 1].

Repository Structure

• src/: Contains the main implementation code.
  • main.ipynb: The Jupyter Notebook containing the Python implementation and visual results of the schemes.
  • holo_chibi.png: Sample image used for testing the cryptographic schemes.
• paper/: Contains the full project report detailing the mathematical background, manual verifications, and critical analysis.
• doc/: Additional project documentation.
• requirement.txt & pyproject.toml: Dependency management files.

Implementation Status & Results

Our implementation focuses on a functional, non-OOP approach to directly translate the paper's mathematical concepts into Python code[cite: 1].

Current progress is as follows:

• 3-out-of-3 scheme: Fully implemented and works as expected[cite: 1].
• $k$-out-of-$k$ scheme (Construction 2): Fully implemented and functioning correctly[cite: 1].
• $k$-out-of-$n$ scheme (Construction 1): Implemented, but currently does not work as expected due to missing mathematical details and confusing nomenclature within the original paper[cite: 1].
• $k$-out-of-$n$ scheme (Construction 2): Not implemented, as it serves as a relaxation of the broken Construction 1[cite: 1].

Tech Stack

The project is built using:

• Python 3.14[cite: 1]
• Jupyter Notebook (for interactive execution and visualization)[cite: 1]
• NumPy (for efficient array and matrix handling)[cite: 1]
• Matplotlib (for plotting and rendering the visual shares)[cite: 1]
• Galois (for finite field arithmetic)[cite: 1]

Getting Started

To run the implementation locally, follow these steps:

1. Clone the repository:

   git clone https://github.com/Kvan0005/INFO-F514-Project
   cd INFO-F514-Project

2. Install dependencies: Using pip and the provided requirements file:

    pip install -r requirement.txt
    ```

3.  **Run the notebook:**
    Navigate to the source folder and launch Jupyter:
    ```bash
    cd src
    jupyter notebook main.ipynb
    ```

## Authors
**Group U (ULB - INFOF514 - 2026)**
*   Erwan Reynders
*   Theo Deville
*   Tristan Bricusse
*   Kevin Vandervaeren
*   Nkweya Tofeun Constance