Quantum Key Distribution (QKD) Simulation: BB84 Protocol

This project is a simulation of the BB84 Quantum Key Distribution protocol developed for the Quantum Information Processing course I followed at Politecnico di Milano.
The BB84 protocol, introduced by Charles Bennett and Gilles Brassard, is a foundational quantum cryptography method, utilizing the unique properties of quantum mechanics to securely establish encryption keys between two parties.

Overview

In this simulation:

• Alice and Bob are the two parties aiming to establish a secure key.
• Eve acts as a potential eavesdropper, trying to intercept the key exchange.
• The protocol demonstrates how quantum mechanics, specifically the No Cloning Theorem and qubit superposition, enables detection of eavesdropping attempts.

For a comprehensive understanding of the project, refer to the full project report, which includes:

• Detailed protocol mechanics
• Classical cryptography background
• Simulation examples for ideal conditions and eavesdropped scenarios

Installation

To run this simulation, ensure you have:

• Python 3.10+ installed on your device. You can download Python here.

Then download the repository as a ZIP file.

Running the Simulation

1. Server Setup: Start the BB84_server.py, which coordinates the QKD process.
2. Participants:
   • Run BB84_Alice.py and BB84_Bob.py for standard key exchange.
   • Optionally, run BB84_Eve.py to simulate an eavesdropper.
3. Commands: Interact with each component through the Command Line Interface (CLI) to simulate QKD steps.

Example Scenarios

1. Ideal Conditions:

• Alice and Bob exchange qubits over a quantum channel and detect any basis mismatches through a classical channel.
• The shared key is established without interference, ensuring secure encryption.

2. Eavesdropper Present:

• With Eve eavesdropping, any attempt to intercept qubits can disrupts their quantum state, making her presence detectable.
• Alice and Bob identify inconsistencies in the shared key, revealing Eve’s interference.

Documentation and Usage

This project is organized as follows:

• BB84lib.py: Core library for handling qubit states and basis.
• CUlib.py: Utility functions for CLI interaction and communication.
• Server and Client Classes: Control the key distribution process across participants.

For further details, please see the documentation section in the full project report.

License

This project is open-source and available under the MIT License.

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For questions, please refer to the report documentation or open an issue.