Post-quantum computing cybersecurity and the rise of satellite constellations

How do quantum computing, cybersecurity, and laser-based space communications relate - and should we be concerned?

In October 2019, Google published a landmark result in the journal Nature: quantum supremacy. Their processor, Sycamore, leveraged 54-qubits, or quantum bits that are superpositions of classical 0 and 1 bits, in order to perform an otherwise intractable computation. While there's academic debate whether Google's achievement qualifies as quantumly supreme, the fact remains that Sycamore did in 200 seconds what the IBM's Summit, the world's fastest supercomputer, could only perform after several days and clever, but unorthodox, data schemes.

The particular computation performed on Sycamore was a toy problem. However, there's one problem that demands attention: public-key cryptography. Public-keys methods, like RSA, allow safe and open password exchange. Its security typically leans on the factoring problem, the infeasibility of dividing a massive integer into its prime factors. An advanced quantum computer, though, could shatter the math via Shor's Algorithm, rendering our defenses useless. In effect, cybersecurity in a post-quantum era demands a complete paradigm shift.

Nevertheless, quantum computing is a nascent technology, so researchers are preparing quantum-resistant codes. One approach beefs up the old idea of symmetric-keys, where both parties use the same key to decode messages. It's risky to transmit that all-import key across a network as is, but quantum mechanics provides a solution!

Quantum key distribution (QKD) uses a pair of entangled photons to create a tamper-proof information packet to share data. The photons' properties are inseparable, so the very act of measuring one photon causes the other to respond in kind. There is no way to eavesdrop without leaving a trace.

How can we setup QKD? Entangling photons is typically achieved by shining laser through a special crystal, splitting one photon into a pair. The beam could piggyback on current fiber optic networks, but laser degrades in fiber. A noisy QKD signal is indistinguishable from an eavesdropped sample. Yet, in 2019 researchers at Peking University successfully conducted QKD over 50 km, a proof of concept on the local scale. However, for world-wide connectivity, we ought to turn upwards - to space!

A legion of satellites (or drones!) could relay QKD between one another and ground receivers. This idea of free-space laser communication is driving a surge of investment by SpaceX, Boeing, and Amazon, among others, to build satellite constellations to deploy global broadband internet. These constellations could foreseeably then provide the platform for QKD.

SpaceX set the bar in February 2020, completing its fourth Falcon 9 launch to now establish 242 Starlink satellites. The Federal Communications Commission has approved 12000 Starlink satellites, and SpaceX is proposing an additional 30000. Amazon owned Project Kuiper also unveiled in 2019 that they are planning to launch 3000. That's a lot of satellites.

Indeed, according to the European Space Agency in February 2020, the heavens are adorned with 5500 satellites, 2300 of which function. Scientists also estimate one million pieces of debris, mostly rocket scraps, in Earth's orbit. Visualize that space junk ocean, or check out roughly 20000 identified objects here. Astronomers feel the impact; the reflective orbiting bodies antagonizes telescope observations. Security pundits believe the lack of regulation in space could lead to the hacking and collision of eagerly but hastily deployed satellites. And the scientific doomsayer may propose Kessler's Syndrome, where a chain reaction of satellite collisions blankets our atmosphere in shrapnel, isolating Earthbound communication from the Universe.

As we grow our technological tool belt, it's in humanity's best interest to protect ourselves and our planet. Quantum computing, cybersecurity breaches, and a web of satellites won't appear overnight, so we ought to eye the skies above and our security below with caution optimism. For now, stick with choosing strong passwords and encourage business and government to drive technology forward in a responsible manner.

Shervin Sahba is a Physics Ph.D. student at the University of Washington. Shervin studies how to control the flow of light by forecasting its future state, merging methods from computational physics, photonics, and machine learning.