China sends potentially unhackable data using satellites

11 August 2017

China has demonstrated a world first by sending potentially unhackable data over long distances using satellites, which laid out the next generation encryption based on so-called "quantum cryptography.''

Last August, China launched a quantum satellite into space, a move which was called a "notable advance" by the Pentagon.

With the use of the satellite, Chinese researchers at the Quantum Experiments at Space Scale (QUESS) project, were able to transmit secret messages from space to earth at a further distance than ever before.

The technology is known as quantum key distribution (QKD). According to commentators, while typical encryption relied on traditional mathematics and while for now it was more or less adequate and safe from hacking, the development of quantum computing threatened that.

Quantum computing refers to a new era of faster and more powerful computers, and according to current theory they would be able to break current levels of encryption.

That was the reason China was looking to use quantum cryptography for encryption. QKD uses photons the particles which transmit light  to transfer data.

"QKD allows two distant users, who do not share a long secret key initially, to produce a common, random string of secret bits, called a secret key," the researchers explained in a paper published in the journal Nature on Wednesday.

The Chinese experiment got underway last year, when a satellite called Micius (named after an ancient Chinese philosopher) blasted off on top of a Long March rocket. The satellite has a photon receiver, and passes over ground stations at the same time every day, during which times scientists can beam up a stream of photons.

According to the Micius team, their ground-to-space entanglement took place over 500 kilometers, shattering the previous entanglement record (100 kilometers) five-fold. Because atmospheric interference could break the entanglement, the Chinese researchers beamed the entangled photons from a ground station in Tibet located more than 4,000 meters above sea level. The results weren't perfect, though; only 911 photons got through to space, out of millions of photons sent.

''This is remarkable on many levels: a 500 km distance, the challenges of stabilizing and tracking the satellite, and atmospheric turbulence,'' said Shellee Dyer, a member of the faint photonics group at the US National Institute of Standards and Technology, in an e-mail. ''I am not aware of any specific US research that focuses specifically on ground-to-satellite quantum teleportation, [although] there have been experiments demonstrating quantum teleportation and pushing the limits of distance.''

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