What Is Quantum Encryption, How Does It Work, and Will It Save Us From Cybercriminals?

APRIL 30TH, 2024
Aftab Alam
Executive Vice President, Product Management

The advent of artificial intelligence (AI) has put new weapons in the hands of cybercriminals and new defensive tools in the hands of those trying to keep them at bay. In this fast-changing landscape, quantum encryption is emerging as a groundbreaking technology with the potential to revolutionize data protection against threats like ransomware. It can’t come soon enough, given that 66 percent of organizations were hit by ransomware last year, and 76 percent of attacks resulted in encrypted data.

Quantum Mechanics in Computing

Before we look at quantum encryption and its applications, let’s dive into its foundational technology, quantum cryptography. TechTarget describes quantum cryptography as “a method of encryption that uses naturally occurring properties of quantum mechanics to secure and transmit data in a way that cannot be hacked.”  

While quantum cryptography focuses specifically on securing data by leveraging quantum mechanics to detect intrusions, quantum computing—another subset of quantum cryptography based on the same mechanics—does so to solve complex computational problems. 

Quantum encryption employs quantum mechanics to perform cryptographic tasks that enhance the security of transmitted data. Unlike traditional encryption methods like AES and RSA Security, which rely on complex mathematical calculations to deter hackers, quantum encryption takes advantage of the physical properties of quantum bits (qubits) to secure data, making it virtually unbreakable by today’s conventional decryption methods. 

The Three Fundamental Principles of Quantum Mechanics in Encryption

Quantum encryption is based on three phenomena unique to the quantum environment:

1. Superposition: Enabling Two Simultaneous States

In quantum encryption, information is encoded into qubits. Unlike conventional binary bits that are either 0 or 1, qubits can simultaneously exist in a state of 0, 1, or any quantum superposition of these states. The Quantum Atlas likens qubits to a light dimmer. So, while a standard light is binary (off or on), a qubit can be at any brightness level between entirely off and entirely on. 

The exact position of the dimmer—how close it is to either 0 or 1—is determined by complex numbers represented by α and 𝛽. These numbers are coefficients in the superposition state equation, typically represented as:


This equation represents the probability of finding a qubit in the “0” or “1” position when it is measured, with α representing the probability amplitude for the state 0 and 𝛽 representing the probability amplitude for the state 1. Together, ∣0⟩ and β∣1⟩ represent the two fundamental states a qubit can be in, which are the quantum equivalents of the binary states in classical computing.

Before it is measured, the qubit exists in both states simultaneously. This allows the qubit to hold much more information than a binary bit, which is why quantum computers are so powerful.

2. Entanglement: Connected Particles, Connected States

Quantum entanglement is a special connection between pairs or groups of particles or where the state of one is directly tied to the state of the other, no matter how far apart they are. This is one of the most non-intuitive concepts related to quantum mechanics and can be challenging to understand. Think of it as two dancers moving perfectly in sync, mirroring each other’s actions, no matter where they are in relation to each other.

For example, imagine two entangled qubits. If one qubit is measured and found to be in a state representing ‘0’, the other qubit will instantly be in the state representing 1, and vice versa. Here’s another metaphor to help you wrap your head around the concept: Imagine flipping a coin that splits in two. If one side lands heads up, the other will always instantly be tails.

In quantum encryption, this instant connection helps detect if someone is trying to eavesdrop or interfere with the sent data. If an outsider tries to view the qubits, the perfect sync between the entangled pairs will be disturbed. That alerts users that their secure channel may be compromised.

3. No-Cloning Theorem

The no-cloning theorem is a rule in quantum mechanics that states that you cannot make an exact copy of an unknown quantum state. Here’s another metaphor to help you understand this concept: Imagine a book in which the story changes every time you read it. If you tried to copy the book to keep the story from changing, your copy won’t capture the story accurately and may have pages from different versions.

In quantum mechanics, this principle means that if a user—say, a hacker—tries to intercept a copy of a qubit to learn its state, they can’t do so without changing the state of the original qubit. This change alerts the original communicators that someone is trying to spy on them. That makes it impossible to copy qubits secretly, effectively protecting information in quantum communications. 

These three quantum mechanical principles—superposition, entanglement, and the no-cloning theorem—provide quantum encryption with a level of security fundamentally unachievable by classical cryptographic methods. This makes quantum encryption a uniquely powerful technology for secure communications, especially as we approach the era of quantum computing.

Quantum Key Distribution: Data Protection Using Quantum Mechanics

Quantum Key Distribution (QKD) employs quantum mechanics to ensure data shared between two parties can’t be decrypted by a third party—a cybercriminal, for example. QKD enables the parties to create a shared random key known only to them, which can then be used to encrypt and decrypt messages. This process ensures any attempt at intercepting the key will be detected. 

Here’s a breakdown of each step involved with QKD. The characters Alice and Bob—coined by the researchers behind the 1978 paper “A Method for Obtaining Digital Signatures and Public-Key Cryptosystems”—represent the two parties communicating.

1. Key Creation and Transmission

The process starts by creating qubits, each representing a bit of the key encoded in a quantum property like polarization or spin. 

In polarization, photons (light particles) are polarized on a linear or circular basis. Linear polarization polarizes photons in a specific direction—vertical, horizontal, or diagonal—with each direction representing different bit values. In circular polarization, the photon's electric field rotates in a circle as it moves forward in either a clockwise or counterclockwise direction. In QKD, right-handed polarization (RHC) and left-handed polarization (LHC) can also encode data. 

For example, Alice randomly chooses a polarization for each photon sent to Bob through a quantum channel—the quantum equivalent of a classical communication channel. These are specifically designed to handle and preserve the quantum mechanical properties of the particles used in quantum communications, such as superposition and entanglement. 

Alice might also randomly switch between polarization bases (linear or diagonal) for each photon. 

Spin, another fundamental property of particles like electrons and protons can also be applied to photons.This is described as spin angular momentum carried by quantum particles. Particles such as electrons have two basic spin states: spin-up and spin-down. This can represent binary data, much like 0 and 1. The spin state of a particle can be manipulated and measured using magnetic fields in specialized devices, spatially separating particles based on their spin states.

For example, similar to polarization, Alice encodes bits of key information into the spin states of particles (like electrons) and sends them to Bob. 

2. Interception Check

Bob is unaware of Alice's basis for each photon, so he randomly chooses a measuring basis once he receives the qubits. Then, both reveal their bases—but not the results—and only keep the results of the photons measured in matching bases. Bob measures the spin states using the appropriate quantum detectors, and both compare their measurement setting to identify the key.

Bob’s measurements collapse the quantum states into classical bits. If no eavesdropping has occurred, Bob’s measurements and the states sent by Alice should theoretically align perfectly. Any eavesdropper— Eve is the name coined in the 1978 paper—trying to intercept the qubits would need to measure them. 

That action would trigger changes in the qubits’ quantum states, as described in the no-cloning theorem. This change would increase the error rate in the measurements noted by Bob compared to the states sent by Alice, with a higher error rate indicating potential eavesdropping (by Eve).

3. Key Sifting and Finalization

Once all qubits are transmitted and measured, Alice and Bob communicate over a classical channel to compare their results for a subset of the transmitted qubits to estimate the error rates. This step is crucial in determining whether the key is safe to use. 

This is all accomplished without Bob and Alice exposing the actual key bits. Instead, they share the bases or settings used in the measurements to check for discrepancies caused by eavesdropping. If the error rate is within acceptable limits—which implies the information has not been compromised—Alice and Bob correct any errors in their respective part of the key, using classical error correction techniques.

Next, privacy amplification is performed. This post-processing step shortens the key and deletes any information an eavesdropper might have captured about the final secret key, further tightening security.

The resulting key, now confirmed by both parties as error-free, is used as a secret key for secure encryption of messages between Alice and Bob. Any attempt to intercept future communications encrypted with this key would require access to the quantum key known only to Alice and Bob.

Will Quantum Encryption Save Us From Cybercriminals?

The jury is out on the long-term results, but even the power of quantum computing—which threatens classical encryption methods—can’t break quantum encryption. Think of it this way: quantum encryption leverages quantum mechanics' unpredictable and unintuitive behaviors to offer a new level of security in data transmission. That makes it a vital technology for safeguarding sensitive data in our increasingly digital world.

Find Out What You Can Do to Better Protect Your Data Today

While quantum encryption is still emerging, you must take action now by choosing data protection solutions that safeguard your data against growing threats like ransomware. 

Get expert help by choosing an Arcserve Technology Partner.

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