⚛️ quantum physics

Power Network SCADA Quantum Communications: A Comparison of BB84, B92, E91, and SGS04 Quantum Key Distribution Protocols

This paper evaluates the performance of BB84, B92, E91, and SARG04 Quantum Key Distribution protocols when applied to large-scale power network SCADA datasets, aiming to address practical challenges in securing real-time data transmission within the availability-prioritized cybersecurity framework of electric power systems.

Original authors: Hillol Biswas, Kyriakos Zoiros

Published 2026-03-03

📖 5 min read🧠 Deep dive

CC BY 4.0

Original authors: Hillol Biswas, Kyriakos Zoiros

Original paper licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

The Big Picture: Securing the Power Grid with "Magic" Light

Imagine the electrical grid as a massive, nervous system for a city. It's not just wires carrying electricity; it's a digital brain (called SCADA) that constantly talks to power plants, substations, and transformers to keep the lights on. This brain sends millions of messages every second.

The problem? Hackers are getting smarter. They want to sneak into this nervous system, lie about the data, or shut things down. Traditional digital locks (like passwords and encryption) are like sturdy padlocks. But with the rise of Quantum Computers (super-fast computers of the future), these padlocks might one day be picked in seconds.

This paper asks: How do we build a lock that even a quantum computer can't pick?

The answer lies in Quantum Key Distribution (QKD). Think of this not as a lock, but as a "magic messenger" made of light particles (photons) traveling through fiber-optic cables.

The Core Concept: The "Glass House" Analogy

In the quantum world, there is a rule called the No-Cloning Theorem. Imagine you have a fragile glass sculpture. If you try to make a perfect copy of it, the original must break or change in the process. You can't steal the secret without leaving a fingerprint.

In this paper, the authors are testing four different "magic messenger" protocols (BB84, B92, E91, and SGS04) to see which one is the best at sending secret keys to protect the power grid.

The Four Contenders (The Protocols)

The researchers simulated these four methods using a giant dataset of real power grid traffic (over 2.5 million records!). Here is how they stack up, using simple metaphors:

1. BB84 (The Classic "Two-Box" Game)

How it works: Imagine Alice sends Bob a series of balls. Some are in red boxes, some in blue. She tells him which box to look in after he catches them.
The Result: It generates a lot of keys (high volume), but it's a bit messy. In the simulation, it produced many keys that didn't match up perfectly, meaning it had a high "error rate." It's like a factory that makes a million toys, but half of them are broken.
Verdict: Good for volume, but not the most reliable for a critical system like a power grid.

2. B92 (The "Simplified" Version)

How it works: This is like BB84 but stripped down. Instead of two types of boxes, it uses just two specific types of balls. It's simpler and faster to set up.
The Result: It was very consistent. Almost every key matched perfectly (low error). However, it didn't generate as many keys as BB84.
Verdict: A solid, reliable worker, but maybe a bit slow if you need to process massive amounts of data quickly.

3. E91 (The "Entangled Twins" - The Winner)

How it works: This is the most "magical." Imagine Alice and Bob each hold one half of a pair of "entangled" dice. No matter how far apart they are, if Alice rolls a 6, Bob's die instantly shows a 6. They don't need to talk to know the result; they just know.
The Result: This was the champion of the study. It produced keys that were large, perfectly matched, and had almost zero errors. Because it relies on "spooky action at a distance" (entanglement), it is incredibly hard for a hacker to intercept without breaking the connection entirely.
Verdict: The gold standard. It's the most secure and reliable for keeping the power grid running smoothly.

4. SGS04 (The "Two-Way" Trip)

How it works: Instead of sending a message one way, the messenger goes from Alice to Bob, and then Bob sends it back to Alice. It's a round-trip ticket.
The Result: This was the weakest performer. Because the message travels twice, there are twice as many chances for it to get messed up or intercepted. The keys often didn't match.
Verdict: Too complicated and prone to errors for this specific job.

Why Does This Matter for the Power Grid?

In regular computer security, we worry about Confidentiality (keeping secrets) and Integrity (keeping data accurate). But for a power grid, the most important thing is Availability (keeping the lights on, 24/7).

If a security system is so complex that it slows down the grid or causes the lights to flicker, it's a failure.

The Study's Finding: The E91 protocol is the best fit because it balances high security with high reliability. It ensures that the "magic messenger" doesn't get lost or confused, keeping the grid stable.

The "Fiber Optic" Highway

The paper emphasizes that this isn't just theoretical science fiction. It uses optical fiber cables (the same ones that bring you high-speed internet).

The Advantage: These cables are already buried underground or strung on power lines. They are immune to electromagnetic interference (like lightning or radio waves) and are perfect for carrying these delicate "quantum" light particles.
The Future: The authors suggest that in the near future, power companies can plug these quantum systems into their existing fiber networks to create an "unhackable" layer of protection for the grid.

Summary: The Takeaway

Imagine the power grid is a castle.

Old Security: Wooden gates and stone walls (easily broken by future quantum computers).
This Paper's Solution: A magical, invisible force field made of light.
The Winner: The E91 protocol is the strongest force field. It uses "entangled twins" to ensure that if a hacker tries to peek, the force field shatters instantly, alerting the guards before any damage is done.

The paper concludes that by using these quantum methods on existing fiber-optic cables, we can build a power grid that is ready for the future, keeping the lights on even in the face of the most advanced cyber threats.

1. Problem Statement

The integration of Supervisory Control and Data Acquisition (SCADA) systems into modern smart grids has created a critical need for robust cybersecurity. Traditional power network security relies on the CIA triad (Confidentiality, Integrity, Availability), but in operational technology (OT) environments like power grids, Availability is often the highest priority (AIC model).

Vulnerability: Current SCADA protocols (e.g., IEC 60870-5-104, DNP3, Modbus) are susceptible to cyberattacks, and classical encryption methods (like RSA) are threatened by the advent of quantum computing (specifically Shor's and Grover's algorithms).
Gap: While Quantum Key Distribution (QKD) offers theoretically unbreakable security based on the laws of physics, there is a lack of practical research comparing specific QKD protocols (BB84, B92, E91, SARG04) when applied to real-world, multivariate SCADA datasets transmitted over optical fiber networks. Existing studies often focus on theoretical security proofs or small-scale simulations without addressing the complexity of large-scale power system telemetry.

2. Methodology

The authors conducted a comparative simulation study using Qiskit (IBM's quantum computing framework) and Google Colab to evaluate four distinct QKD protocols against real SCADA data.

Dataset: The study utilized the PNNL (Pacific Northwest National Laboratory) Electricity and Natural Gas System Dataset (specifically "Day 3"), which contains over 2.5 million records. The data was converted from PCAP (packet capture) files to CSV, extracting six specific fields representing SCADA telemetry variables.
Simulation Environment:
- Data Preprocessing: Classical SCADA features were normalized (0–1 scaling) and encoded into quantum states using Angle Encoding (rotating qubits along the Y-axis of the Bloch sphere based on normalized values).
- Quantum Circuits: Custom quantum circuits were designed for each protocol:
  - BB84: Uses two conjugate bases (+ and ×) for encoding and measurement.
  - B92: Uses two non-orthogonal states for streamlined key generation.
  - E91: An entanglement-based protocol utilizing Bell inequality tests for security verification.
  - SARG04 (SGS04): A two-way deterministic protocol designed to resist Photon Number Splitting (PNS) attacks.
- Process Flow: The simulation involved encoding features $\rightarrow$ key exchange (simulating Alice, Bob, and potential eavesdropper "Eve") $\rightarrow$ error correction/privacy amplification $\rightarrow$ decryption and comparison.
Evaluation Metrics: The performance of each protocol was assessed based on:
- Key Size: The length of the generated secure key.
- Key Match Rate: The percentage of times Alice's and Bob's keys matched perfectly.
- Quantum Bit Error Rate (QBER): A metric indicating noise or eavesdropping; lower is better.
- Composite Performance Index: A weighted analysis of the above metrics.

3. Key Contributions

Real-World Data Application: Unlike many theoretical papers, this work applies QKD protocols to a massive, multivariate, real-world SCADA dataset, bridging the gap between quantum theory and power system operations.
Comparative Analysis: It provides a direct, empirical comparison of four major QKD protocols (BB84, B92, E91, SARG04) under identical simulation conditions using optical fiber parameters.
Protocol Optimization for OT: The study identifies which protocol is best suited for the specific constraints of power grids (high availability, low latency, and strict error tolerance).
IEC 62351 Alignment: The framework maps QKD outputs (QBER, session keys) to the IEC 62351 standard for power system cybersecurity, proposing a "physical-layer trust metric" before traditional encryption.

4. Results

The simulation results, derived from the first 100 samples of the dataset, revealed distinct performance characteristics for each protocol:

BB84: Generated large key sizes but suffered from a low match rate and high QBER (up to 0.50 in samples). This indicates that while it generates many bits, a significant portion is unreliable due to noise or protocol inefficiencies in this specific encoding context, leading to frequent key rejections.
B92: Demonstrated high robustness with a perfect match rate (100%) and zero QBER in the samples. However, it produced slightly smaller key sizes compared to others, trading throughput for reliability.
SARG04 (SGS04): Performed poorly across all metrics, showing low key agreement and high inconsistency, making it less suitable for this specific SCADA application.
E91 (Entanglement-based): Emerged as the superior protocol.
- Performance: Achieved the largest average key size while maintaining a 100% key match rate and 0.0 QBER.
- Security: Leveraged Bell inequality violations (CHSH inequality) to detect eavesdropping via the loss of entanglement, offering a unique physical-layer security check distinct from error-rate detection used by other protocols.
- Conclusion: E91 provided the best balance of throughput, consistency, and security, making it the most dependable option for SCADA traffic.

5. Significance and Future Outlook

Critical Infrastructure Protection: The study validates that optical fiber-based QKD is a viable solution for securing national critical information infrastructures (CII) like power grids. It addresses the "Availability" priority of the AIC model by ensuring continuous, low-latency key refreshment.
Physical-Layer Security: By using QBER and Bell violations as trust metrics, the system can detect intrusions at the physical layer before data encryption occurs, offering a proactive defense mechanism against sophisticated cyberattacks.
Implementation Pathway: The work outlines a clear path for deploying QKD in existing utility fiber networks (e.g., OPGW cables), suggesting that the infrastructure is already in place for such upgrades.
Future Work: The authors plan to transition from simulation to real quantum hardware and integrate Quantum Machine Learning (QML) to handle even larger datasets, simulating a full-scale real-world deployment.

In summary, this paper demonstrates that E91 is the most effective QKD protocol for securing Power Network SCADA systems, offering a robust, high-throughput, and physically secure method to protect critical energy infrastructure against both classical and quantum-era cyber threats.