Quantum Keys for Classic Codes: China's New Satellite

Beijing’s recent quantum satellite launch gives us a glimpse at the future of secure communications.

By Jacob L. Shapiro

China's quantum satellite - nicknamed Micius after a fifth century BC Chinese scientist - blasts off from the Jiuquan satellite launch center in China's northwest Gansu province on Aug. 16, 2016. STR/AFP/Getty Images

China announced on Aug. 16 that it had successfully launched the world’s first quantum satellite. The technical name of the satellite is Quantum Experiments at Space Scale (QUESS), and according to Xinhua News Agency, the satellite will establish “ultra-secure quantum communications” that will be “un-crackable.” China Daily noted it was just the first step toward China’s goal of creating a space-based unbreakable quantum communications system by roughly 2030.

QUESS is going to be performing a variety of experiments over the course of its two-year mission. One will be conducted in conjunction with the Austrian Academy of Sciences and will test the phenomenon known as quantum entanglement. Another will be an attempt to set up extremely secure communication between Beijing and Urumqi in Xinjiang province using what is called Quantum Key Distribution.

Quantum entanglement is what makes all of this possible. It is possible to “entangle” two very small particles, meaning that the two particles share physical properties. When a feature of one particle is measured, the other particle’s corresponding feature is instantly known, no matter how far away the two particles have been moved from each other. Einstein famously called this phenomenon “spooky action at a distance.”

Quantum communication as we understand it today means that, if both sides’ equipment is properly set up (which is by no means an easy thing to do, as Chinese scientists have noted), they can share access to a large set of entangled particles.

What we are really talking about is Quantum Key Distribution (QKD), which proposes to use some of the peculiar phenomena observed in the behavior of entangled particles to develop keys that are extremely difficult if not impossible to hack or steal. Due to the unique attributes of entangled particles, anyone attempting to intercept the message would cause it to, in effect, self-destruct.

If the Chinese are successful in their experiment, they will still use a code and a key to communicate between Beijing and Urumqi. The novel part of this will be that the code it uses will have a key generated by QKD beamed down from a satellite orbiting the earth.

Much has been made of the notion that China’s quantum satellite means China is on its way to creating an unbreakable communication system. However, unbreakable codes already exist. The encryption technique known as the one-time pad (OTP), if done correctly, is mathematically unbreakable.

The problem with OTP is that it is horribly inconvenient. For it to work, the key must be truly random, must be at least as long as the text being transmitted, must never be reused and must remain secret. Assuming the two sides trying to communicate are not in the same place, that means you also must somehow get the key from one place to another without it being intercepted. OTP is 100 percent secure, but executing it is extremely difficult. So difficult, in fact, that scientists suggest that it is easier to shoot a satellite into space and use it to beam down entangled photons to different stations equipped to receive them.

Many of the codes used for covert communication are themselves quiet secure. The reason QKD is so attractive is because, to a degree, it mitigates the biggest security liability in the equation: human frailty. Still, it hardly eliminates this vulnerability altogether. The satellite could conceivably be hacked, or the person on one receiving end of the entangled particles could be followed or coerced into giving up the information.

The reason China and others are looking to space is because of one of the key limitations in employing this technology right now. Dr. Ned Allen, chief scientist for Lockheed Martin, told the Center for Strategic and International Studies that the biggest problem when it comes to using QKD for communication is the degradation of the signal over distance. You cannot employ an amplifier to boost the signal because that would have the same effect to the signal as someone attempting to steal it and result in the destruction of the message.

One of the things the Chinese are testing with this satellite is whether, as they suspect, there will be less signal interference between a space-based satellite and an earth-based station than there would be between two points far away from each other on earth, whether transmitting through fiber optic cables or some other means.

Behind all of this is the question of whether Beijing is going to be able to continue investing in this kind of research and technology over the course of the next 20 years. The chief scientists of the QUESS project told China Daily that, if QUESS does well and China sends more of these satellites into orbit, a global network of communication using QKD could be set up around 2030. China has been investing much more money in its space program and research than it did in the past. Funding for basic research doubled from 2005 to 2015, and an OECD report said that China’s space program’s budget was approaching $11 billion as of 2013. For a point of reference, NASA's 2015 budget was roughly $18 billion.

That investment growth came as China was in the throes of its growth miracle. The Chinese economy is now slowing down and the government is attempting to pull off a massive economic transition without much precedence for success. As China’s economy slows down, the question will become whether these types of endeavors remain a priority for the Chinese government, or whether they will be seen as wasteful drains of money that could be better used in other parts of the country.

Still, for now, as the U.S. relies more and more on private companies instead of NASA for the future of some of its space operations, it seems that the Chinese and their strong, centralized push can yield impressive results on sophisticated space-based operations in a very short time period.

I am not a scientist, nor a cryptologist. But one does not have to be either, I think, to understand what quantum communication is and what China’s launch of QUESS means. This is not a breakthrough that puts Beijing in first place in a race for the domination of space (the Europeans, Russians and U.S. are all working on this too), or even the imminent development of an impenetrable communication system. It does, however, speak well of the Chinese space and quantum research programs, and gives us a glimpse into what the future of communications looks like on, and increasingly off, this planet.

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