China gets closer to totally hack-proof comms

A Chinese team has just succeeded in the satellite transmission of a “secret” encryption key between two ground situations located roughly 700 miles apart.

So why, you may ask, is this big news?

It’s down to a concept physicists call quantum entanglement. Putting it to work, Chinese scientists seem to have established the first truly unbreakable link between a satellite and its terrestrial controllers. It raises the possibility of a ​theoretical “100%” secure global communications network, with China in the driving seat in its development.

Here’s a rundown of what it all means – and why cyber security enthusiasts should care.

Background: quantum computing in a nutshell

• All computers rely on the ability to store and manipulate information.
• The computers we all use right now manipulate individual bits, which are basically binary switches: they can either be in the off position (0), or in the one position (1).
• Rather than bits, quantum computers manipulate data via qubits. As well as being on or off, qubits can also be in ‘superposition’, where they are both on and off at the same time, or else somewhere in the spectrum between the two states.
• If a standard computer is instructed to find a correct solution from multiple alternatives, it will generally explore each option in turn, until the right one is discovered. Quantum computers are able to consider every option at once.
• Even compared to today’s most powerful supercomputers, quantum computing opens up the possibility of much faster processing, massively enhanced problem-solving capabilities, including the ability to analyse uncertainty.
• Quantum computing may enable the rapid acceleration of artificial intelligence development. It could also allow developers to simulate complex and uncertain scenarios. Possible uses include gaining a better understanding of disease pathology and predicting the behaviour of people and markets.
• So far, the theories surrounding quantum computers have advanced farther than the actual hardware. Companies (e.g. Google and IBM) as well as nation states are all involved in what has been dubbed the quantum arms race: the competition to build the first usable, stable quantum computer.

Quantum computing and the threat to encryption

• The idea behind encryption is simple enough: data is encrypted (i.e. scrambled), and can only be turned back into a readable form if you have access to the right encryption key. 
• In theory, any encryption key can be hacked. However, in reality, so long as you have a fit-for-purpose encryption system in place that uses a suitably strong algorithm, cracking the code with even an ultra-powerful standard computer is a practical impossibility.
• Quantum computing could be a gamechanger. Cracking an encryption code involves breaking down a vast number of problems. A standard computer has to solve these problems one at a time. By contrast, quantum computing enables thousands of problems to be solved simultaneously. Theoretically, an encryption key that would take many months to crack on a standard computer could be hackable in hours with a quantum computer.

The solution: quantum key distribution

Quantum computing poses a threat to encryption. That said, quantum physics may offer an answer…

• Quantum key distribution (QKD) is based on a particle physics principle known as quantum entanglement. Under this principle, where you have a pair of twinned light particles (photons), the properties of those two photons remain identical to each other, no matter how far apart those particles are. 
• So if you use one of those entangled particles to create an encryption key, only the person with the other particle can decode them.
• Any attempt to interfere with or intercept the quantum key will prevent that key from working.
• So how do you distribute your quantum key from A to B? It’s possible to do it via fiber optic cable. However, optical fibers are susceptible to interference. Also, transmission over ultralong distance relies on intermediate repeaters to boost the signal. In fact, so far, the longest recorded distance for successfully distributing a quantum key via a cable is just 62 miles.
• Chinese quantum physicist, Pan Jianwei has been working on the distribution of quantum keys via satellite. To this end, China has also built Micius, a satellite designed specifically for quantum communications research.

The latest development

In 2017, Micius was used to set up a quantum key link between ground stations in Vienna and Beijing. However, in that case, Micius had to actually generate and distribute the encryption keys.

This year, Micius was used to send a secret key between two ground stations at Delingha and Urumqi, separated by around 700 miles. The satellite merely acted as a blind transmitter, with no information about the key.

The efficiency of the transmission was increased by fourfold compared to previous experiments. What’s more, the error rate in transmission was such that any attempt to eavesdrop on the message would be isolated from general noise and flagged up.

What it means

It’s important to remember that we’re still a long way from existing encryption methods being rendered redundant.

That said, the research shows that it is technically feasible to distribute a quantum key between two stations via satellite, and without that satellite having any information about the key. In other words, it’s a theoretical “100%” point-to-point secure transmission with the possibility of successful interception ruled out.