OPTOELECTRONICS
A new era of secure communication
The role of quantum encryption optic networks
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n the ever-evolving landscape of digital communication, the need for robust security mechanisms is paramount. Traditional encryption methods, while effective to a degree, are increasingly vulnerable to sophisticated cyber-attacks and the advent of quantum computing. This has spurred the development of quantum encryption, Quantum encryption, also known as quantum cryptography, uses the principles of quantum mechanics to protect information. Unlike classical encryption, which relies on complex mathematical algorithms, quantum encryption employs quantum bits or qubits. Qubits can exist in multiple states simultaneously and can be entangled, meaning the state of one qubit can instantly affect the state of another, no matter the distance between them.
Quantum Key Distribution (QKD) is a primary application of quantum encryption. It focuses on securely exchanging encryption keys between parties. The BB84 protocol, developed by Charles Bennett and Gilles Brassard in 1984, is one of the most well-known QKD protocols. In QKD, keys are transmitted using quantum states, ensuring that any attempt at eavesdropping can be detected due to the disturbance it causes to the quantum states.
Fibre optic networks and quantum encryption
Fibre optic cables, which transmit data as light pulses, are ideal for carrying quantum information over long distances with minimal loss and interference.
These cables are inherently more secure than traditional copper cables. They are immune to electromagnetic interference (EMI) the other hand, copper cables are vulnerable to physical tampering, as they can be easily accessed and spliced into, leaving them open to data interception and manipulation. Fibre optics can transmit data over long distances with minimal loss, typically up to 100 km. This is crucial for quantum communication, where maintaining the integrity of quantum states over long
Implementing QKD in optical communications
When implemented in optical networks, QKD keys, ensuring a highly secure communication channel. QKD transmits numerous photons optic cables, creating a stream of qubits. Cryptographic information is encoded into these quantum states, such as photon polarisation or phase.
Any interception by an eavesdropper introduces detectable errors. A robust key distribution protocol can identify these tampering attempts, ensuring the secure generation of shared random keys over the quantum channel.
In a typical QKD setup, the sender A randomly encodes photons using several quantum horizontal, vertical, or diagonal polarisation. The receiver B measures each photon by randomly selecting a measurement basis. After the transmission, A and B publicly share their chosen bases without revealing the measurement results.
This process allows them to identify the subset of B’s measurements that perfectly match the states A prepared, provided their bases align. They retain these correlated
46 SEPTEMBER 2024 | ELECTRONICS FOR ENGINEERS
results to form a shared secret key. If an eavesdropper E intercepts and measures some photons during transmission, the original quantum state is disturbed due to the inherent restrictions of quantum physics. When A and B compare their bases afterward, they will notice a higher error rate in the photons observed by E, signalling potential eavesdropping. They can then discard the compromised key data and repeat the protocol until they achieve a secure key through a quantum channel with no detected tampering.
Real-world applications and
encryption has several practical applications, institutions can use this combination to data, ensuring the privacy and security of their operations.
Similarly, government agencies and defence information and communications, enhancing national security. Businesses can also secure their internal communications and protect intellectual property from advanced cyber threats.
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