Compromised Password Checker (Bloom Filter)

📚 Overview

This project implements a Bloom Filter from scratch to efficiently check whether a password has likely been compromised in a known breach dataset.

Users can enter a password into a simple web form, and the app will check if it exists in a database of breached passwords using a probabilistic Bloom filter structure.

• If found: warns the user that the password might not be safe.
• If not found: reassures the user that the password likely isn't compromised.

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🌐 Live Demo

You can try the app live here: Bloom Filter Password Checker - Live Demo

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🚀 How to Run the Project

1. Install Requirements

Make sure you have Python 3 installed.

Then install Flask:

pip3 install flask

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2. Project Structure

/Compromised-Password-Checker
  |- app.py                 # Flask web server
  |- bloom_filter.py        # Custom Bloom Filter implementation
  |- passwords.txt          # Sample breached password list
  |- templates/
      |- index.html         # Simple web form
  |- README.md              # This file

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3. Run the Application

From the project folder, start the Flask server:

python3 app.py

You should see output like this:

 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

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4. Use the App

• Open your web browser and go to http://127.0.0.1:5000
• Enter a password in the form
• Click "Check"
• See the result!

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⚙️ Technical Details

• Bloom Filter Size: 10,000 bits
• Number of Hash Functions: 5
• Hashing Algorithm: hashlib.sha256
• False Positives: Possible, but false negatives are impossible.

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🔥 Why a Bloom Filter?

• Fast membership tests even with large datasets.
• Memory-efficient compared to storing every password directly.
• Useful for security applications where checking billions of passwords needs to be lightweight.

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📌 Notes

• The full breached password dataset is too large to upload to GitHub. A small sample list is used here for demonstration purposes.
• The Bloom Filter was built from scratch (not using third-party libraries).
• The hashlib Python library is used to create multiple independent hash functions based on sha256.