Analytical-BB84-QKD-Engine

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Analytical-BB84-QKD-Engine

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An interactive BB84 Quantum Key Distribution system built with Qiskit and Streamlit. Features simulator and analytical turbo modes, strategy-aware QBER heatmaps, eavesdropping detection, and secure/abort zone visualization. Designed for education, research, and real-time quantum security analysis.

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# 🔐 Analytical BB84 QKD Engine

### **Team Name:** AnalytiQ  
### **Team Members:** Sumit Tapas Chongder [M25IQT013]
### **Hackathon:** Qiskit Fall Fest 2025  
### **Project:** Analytical Acceleration of the BB84 Protocol — An Interactive Framework for Quantum Key Distribution Security Analysis
### **Achievement:** 🏆 First-Place Winner at Qiskit Fall Fest 2025 Hackathon

---

## Presentation Video

### Drive Link (Video): https://drive.google.com/file/d/1L4MYpVNZV5CoRlqweYxgF_FzWHhgG-TU/view?usp=drive_link

**📽️ Streamlit app demo starts at 5:05 — showcasing the interactive Analytical BB84 QKD Engine in action.**

https://github.com/user-attachments/assets/71ff6d63-e657-4207-ad4e-33f7b60763c4

---

## 📖 Overview

This project presents a complete, interactive implementation of the BB84 Quantum Key Distribution (QKD) protocol using **Qiskit** and **Streamlit**. It demonstrates how two parties (Alice and Bob) can securely generate a shared key while detecting any eavesdropping attempts by Eve. The system features a dual-backend architecture:

- **Simulator Mode** using Qiskit Aer for correctness validation  
- **Analytical Turbo Mode** enables scalable, real-time visualization of Quantum Bit Error Rate (QBER) by replacing gate-level quantum simulation with closed-form probabilistic models that compute ensemble-averaged outcomes across thousands of qubits, eliminating the need for per-qubit gate and measurement simulation.

Users can toggle between multiple Eve strategies
- **DoNothing:** Eve remains passive and does not interfere with the qubits, resulting in no disturbance.
- **Intercept-Resend:** Eve measures each qubit in a fixed basis and resends it, causing significant errors when her basis mismatches Alice’s.
- **Probabilistic Skew:** Eve chooses her measurement basis with a biased probability, introducing subtle errors that are harder to detect.
  
Our app also offers a **stepwise walkthrough** of the **BB84 protocol**, allowing users to observe each phase of quantum key generation and security validation in detail.

Our app includes **strategy-aware dashboards**, **annotated heatmaps**, and **secure/abort zone visualizations** — making quantum security fast, clear, and interactive.

---

## 🚀 Features

- ✅ **Full BB84 protocol workflow:** Alice → Eve → Bob → Sifting → QBER → EC/PA  
- ⚡ **Dual execution modes:** Simulator (Qiskit Aer) and Analytical Turbo Mode
- 🧠 **Eavesdropper simulation:** Intercept-Resend and Probabilistic Skew strategies  
- 📊 **Security phase diagrams:** QBER heatmaps with cyan threshold contours  
- 🔍 **Decoy state analysis:** Signal > Decoy > Vacuum yield ordering  
- 🧪 **Noise modelling:** Depolarizing channel with adjustable parameters  
- 🧰 Modular codebase with caching and reproducibility  
- 🎓 Educational clarity with annotated visuals and interactive UI

---
### 1. Streamlit App Homepage 
🖼️ “Streamlit dashboard for BB84 protocol execution and visualization”

---

## 🧠 Why BB84?

As quantum computers advance, classical encryption methods like RSA and ECC face potential compromise. BB84 offers a physics-based alternative: any attempt to intercept qubits introduces detectable errors. This project makes BB84 tangible through simulation, visualization, and analysis.

### 🔐 BB84 Protocol — 6 Key Steps
- **Alice generates random bits and bases:** 
She creates a sequence of 0s and 1s, and randomly chooses a basis (Z or X) to encode each bit as a quantum state.
- **Alice sends qubits to Bob:**
Each bit is encoded as a qubit — either |0⟩, |1⟩, |+⟩, or |−⟩ and transmitted over a quantum channel.
- **Bob measures each qubit in a random basis:**
Bob doesn’t know Alice’s basis, so he randomly picks Z or X for each qubit and records the result.

![Image](https://github.com/user-attachments/assets/0716a692-3a13-432b-a029-ce6fda6c9e22)

- **Alice and Bob share their basis choices:**
Over a public classical channel, they reveal which basis they used — but not the actual bit values.

![Image](https://github.com/user-attachments/assets/43586a47-ff51-41c7-acdc-f33f96eb4428)

- **Sifting and QBER estimation:**
They keep only the bits where their bases matched (sifted key), then compare a small sample to estimate the Quantum Bit Error Rate (QBER).

![Image](https://github.com/user-attachments/assets/a39987a5-485a-4990-82e3-d36f6dcde965)

- **Error Correction and Privacy Amplification:**
If QBER is low, they correct errors and compress the key to remove any leaked information, resulting in a secure shared key.

---

### 2. BB84 Circuit Diagram

##### 🖼️ “Quantum circuit representation of BB84: Alice prepares qubits, Eve does not intercept, Bob measures”

##### 🖼️ “Quantum circuit representation of BB84: Alice prepares qubits, Eve intercepts (Intercept Resend Attack), Bob measures”

- Intercept-Resend Attack: Eve secretly measures each qubit in a fixed basis (usually Z), then sends a new qubit to Bob — introducing noticeable errors if her basis doesn’t match Alice’s.

##### 🖼️ “Quantum circuit representation of BB84: Alice prepares qubits, Eve intercepts (Probabilistic Skew Attack), Bob measures”

- Probabilistic Skew Attack: Eve randomly chooses her measurement basis with a bias (e.g., 70% Z, 30% X), making her interference harder to detect but still causing subtle errors.

---

## 🛠️ Implementation

### 3. Workflow Flowchart

##### 🖼️ “BB84 protocol workflow: from qubit preparation to key distillation”

### 🔧 Technologies Used
- Python 3.10+  
- Qiskit 2.0+ 
- Streamlit  
- NumPy  
- Matplotlib / Seaborn

---

## 📈 Results

### Error Checking: QBER + Decoy Yields

- We perform error checking by estimating QBER from sifted bits and validating decoy state yields to ensure channel integrity and detect eavesdropping. 
- The Expected Order should be: Signal > Decoy > Vacuum. Deviations can indicate eavesdropping or channel anomalies. Additionally, the QBER value should be less than the Abort threshold (QBER) value; otherwise, QBER aborts.

---

### Comparative Visualizations:

#### 1. QBER vs Intercept Probability
<img width="1647" height="1787" alt="Image" src="https://github.com/user-attachments/assets/9b03ee15-6820-4af4-9b65-c871136b2689" />
   
#### 2. QBER vs Depolarising Noise
<img width="1636" height="1868" alt="Image" src="https://github.com/user-attachments/assets/75eb4097-8d29-4f34-92af-0598e5fc3fcb" />
   
#### 3. QBER vs Probabilistic Skew
<img width="1631" height="1791" alt="Image" src="https://github.com/user-attachments/assets/0dd1d238-dac8-480e-8786-316927993655" />

---

### QBER Heatmap with Threshold Contour

🖼️ “QBER heatmap showing Secure and Abort zones with cyan threshold contour (Intercept Resend Attack)”

🖼️ “QBER heatmap showing Secure and Abort zones with cyan threshold contour (Probability Skew Attack)”

#### Insights: 
- QBER increases with intercept probability and channel noise  
- Cyan contour marks threshold boundary  
- Secure vs Abort zones clearly annotated  
- Decoy yields follow the expected ordering  
- Analytical mode enables instant heatmap generation

---

## 💡 Innovation

- **Turbo Mode:** Analytical backend with vectorized probability model  
- **Strategy-Aware Dashboards:** Compare Eve strategies side-by-side  
- **Secure/Abort Zone Visualization:** Cyan contours + region labels

### 1. Error Correction + Privacy Amplification (Using Vectorized QKD Simulation)

- ✅ Threshold-based modelling: We simulate EC and PA using a configurable QBER threshold (e.g., 11%) to decide whether the protocol proceeds or aborts.
- 🧮 Error Correction (EC): If QBER is below the threshold, we assume classical error correction succeeds and mismatched bits are reconciled.
- 🔐 Privacy Amplification (PA): We reduce the final key length based on estimated information leakage.
- ⚡ Vectorized simulation: This approach avoids slow bit-level operations and enables fast, scalable analysis across many parameter settings.
- 📊 Real-time feedback: Users instantly see whether EC/PA succeeds and how much usable key material remains.

### 2. Eve Strategy Comparison

🖼️ “Side-by-side heatmaps for Intercept-Resend and Probabilistic Skew strategies”

---

## 🎓 Educational Value

This app is designed to teach QKD interactively:
- Visualizes quantum disturbance and eavesdropping detection  
- Compares QKD to post-quantum cryptography (PQC)  
- Ideal for students, researchers, and hackathon judges

---

## 📦 Installation and Execution

## Install miniconda
##### Windows Command Prompt
curl https://repo.anaconda.com/miniconda/Miniconda3-latest-Windows-x86_64.exe -o .\miniconda.exe \
start /wait "" .\miniconda.exe /S \
del .\miniconda.exe

##### macOS
mkdir -p ~/miniconda3 \
curl https://repo.anaconda.com/miniconda/Miniconda3-latest-MacOSX-arm64.sh -o ~/miniconda3/miniconda.sh \
bash ~/miniconda3/miniconda.sh -b -u -p ~/miniconda3 \
rm ~/miniconda3/miniconda.sh

##### Linux
https://www.anaconda.com/docs/getting-started/miniconda/install#linux-2

In case of any future updates, you can check the following link for Qiskit installation.\
https://quantum.cloud.ibm.com/docs/en/guides/install-qiskit

## Install environment
Download qcl.yml \
Open Anaconda prompt (Windows) \
Open terminal (macOS and Linux)

#### Change the directory where the qcl.yml is downloaded

#### conda env create -f qcl.yml

## Activate Environment and Run the Streamlit.py Application
Activate the qcl Environment by using the following command:
##### conda activate qcl

Change the directory where you have downloaded the Python File (streamlit_app.py)
For Example:
##### cd Downloads {if the python (.py) file in the Downloads Folder}

To run the streamlit_app.py, execute the following command
#### streamlit run streamlit_app.py

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