Four things you should know about Quantum Encryption

What is Quantum Encryption?
 

Encryption uses a set of mathematical instructions (an algorithm) paired with a key to jumble messages, making them seem nonsensical to anyone who doesn’t have the key. The security of this method depends on how easy it is to steal the key - once the key has been intercepted, the message can be decoded.

Quantum Encryption can completely secure the key, and hence the underlying message. Unlike other encryption tools that are based on mathematics, it uses fundamental laws of physics instead.

The key to the message is locked within a tiny particle of light called a photon, Professor Ling says. The laws of physics are such that if someone intercepts a photon in motion, it changes itself and cannot be used to decrypt the messages.

“The key is encoded behind the state of the photon so it becomes very difficult for eavesdroppers to hack. If someone tries to tamper with an individual photon, its properties are changed immediately,” he explains.
 

Why is it important?

Quantum keys can be safely sent through regular fiber optic cables used for telephone, internet and television signals. “There is no other mechanism by which we can share encryption through public channels like optical fibre and still have the guarantee that no one has tampered with it,” he said.

Any attempt to hack a quantum key can also be immediately detected. “It distributes the encryption key in a way that can detect efforts at tampering and eavesdropping.”

The physics behind this is called “quantum entanglement”. The photons are produced in pairs - one is kept by the message’s sender and another is sent with the key. The receiver can tell if the key was intercepted by comparing the properties of these two photons.

“You can think of the two particles as twins,” he said. “This correlation is reduced if an external mechanism comes and taps into [one of the photons]. We just have to compare quality of correlation to detect if a particle has been disturbed,” he said.
 

How could it affect government?

Quantum Encryption would raise the level of privacy for any government communication - whether they are diplomatic talks between governments or agencies like hospitals sharing citizens’ personal healthcare records.

Online voting could - as in Switzerland - finally be secure. It has been held back for years’ because of cyber security concerns.

With quantum key systems already available off-the-shelf, even citizens could use these between their home and work. “For a city like Singapore, for example, where fibre penetration is high in residential areas, it is not unforeseeable”, he said.

Governments could also have to deal with new kinds of businesses which sell photons to customer. “We are seeing interest from telecommunications companies who want to sell photons to end users. You and I can just receive the photons from the service provider and that simplifies the material cost.”

But the technology could also make it harder for government to access citizens’ communications: an ongoing debate as officials seek to track potential terrorists.

What is happening in the region on this?

The Singapore government is funding academics to work on a global quantum network linking cities together. Professor Ling and his research group are also working on a new way to transport quantum keys in space.

“With optical links, there is a distance limit that needs to be overcome. For transmissions within a city the size of Singapore it is not a problem. But over longer distances, like between Singapore and Australia, a single photon will be lost inside the fibre network,” he said.

Their technique uses telescopes and satellites to relay quantum keys over long distances.

Meanwhile, China is building an ambitious 2,000km quantum link between Beijing and Shanghai, he said. The project is being funded by the central government at US$85 million. It is expected to launch this year and will initially be used to transfer money by the Industrial and Commercial Bank of China (ICBC).

While massive quantum networks have caught the fancy of officials, there have been “very few direct applications” in citizen-facing services, Professor Ling says. The Swiss elections from 9 years ago is still the best example for this.

“The technology is already quite mature. It’s really about studying the knowledge about the technology so that government can feel they can use it for public-facing services,” he says.

While Quantum Physics is yet to play a major role in government’s everyday work, these invisible particles of light could change the way people perceive security.