# What you should know about quantum encryption

Jun 25, 2020

Every cipher can be broken. That’s why cybersecurity experts never stop thinking about new ways to encrypt messages. With the rise of quantum computing, these experiments have become even more critical, as new technology could break today’s strongest cryptography algorithms.

But if quantum computing can weaken cybersecurity, quantum encryption can make it infinitely stronger.

## What is quantum encryption?

Quantum encryption, or quantum cryptography, is a method of securing a message using the laws of quantum mechanics.

Quantum computing may seem light years away, but scientists are convinced it’s already on our doorstep. For example, IBM has already created a quantum encryption method that is not vulnerable to quantum computing.

Here’s how it differs from the methods we use now.

Today, we often use asymmetric, or public-key, encryption, where the sender and the recipient have a pair of keys — one public and the other secret. Just like other encryption methods, it's based on a mathematical problem. For example, prime factorization works well for public encryption because it's easy to do one way, but hard the other. So, multiplying two large prime numbers takes only a moment, but deriving those prime numbers from the result is almost impossible. That's why 256-bit public-key encryption algorithms are considered safe for hundreds of years. To know more about public-key encryption, check out this article.

This could be a problem in the quantum computing era. Not only are quantum computers faster, but also operate on a different set of laws. In other words, an algorithm that takes modern computers decades to crack could be solved overnight with quantum computers. Today, scientists are harnessing the power of quantum computing to create unbreakable encryption methods.

## How does quantum encryption work?

In public-key encryption, we must first exchange secret keys and establish a line of communication. In quantum encryption, this would be done with the help of photons or light particles.

What you should know about photons is that they have several distinctive properties, one of them being a spin. The spin has a direction — horizontal, vertical, or diagonal (either from the left or the right). Most importantly, the direction of the spin can be changed when the photon is passed through a filter.

Here’s how it works in practice.

First, the sender turns a message into a binary code, represented by 1s and 0s. The code is then transformed into photons, where 1s are photons with a vertical or a right-side spin, and 0s are photons that have a horizontal or a left-side spin.

The message is encrypted by sending each photon through a randomly selected filter and changing its spin. This is why this type of encryption is so strong: it’s not enough to know the photon’s spin — you also have to know the order in which filters were used. If you get just one of them wrong, it scrambles the whole result.

Quantum encryption has several problems. First, it needs more time. A few decades ago, we were content with using slow, gigantic, and unsecured computers. We thought these machines were incredible because we had nothing to compare them with. But now we do: we know that computers should be fast, reliable, and secure. That’s why before quantum computing can take over, it has to become better than traditional computing. And at the moment, it’s simply not. Here’s why:

- Quantum computing is still new and very expensive. It will take time before regular consumers can afford it.
- Lack of infrastructure. Photons can’t travel very far. So parties must either be connected directly or use relays to increase the range over which the message can be sent.
- Security is not guaranteed. While the quantum encrypted message is theoretically unbreakable, the use of relays and routers could give hackers new opportunities to get the encryption key. That said, China claims to have sent a completely secure message 1200 km through their quantum satellite.

It’s impossible to tell when quantum computing will become widespread, but it’s clear that the wait will be exciting.

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Elisa Armstrong

Verified author

Elisa’s all about languages. She speaks five, loves stand-up comedy, and is writing her first novel. Besides her extensive knowledge of cybersecurity, she’s an expert in persuasion techniques hackers use and strives to teach people how to avoid online scams.