Space agency uses Raspberry Pi to solve satellite encryption puzzle

How does the European Space Agency (ESA) communicate securely with satellites and space missions?

Surprisingly, until relatively recently it often didn’t – something which is still true for smaller, cheaper satellites such as CubeSats.

Now ESA hopes that an experiment consisting of a small module built around a tiny Raspberry Pi Zero board controlled from a laptop on the ground will close this hypothetical security issue at very low cost.

It’s called the Cryptography ICE Cube (or CryptIC), measures only 10x10x10cm, and is the brainchild of a special ESA department called the International Commercial Experiments service, or ICE Cubes for short.

Currently installed on the Cygnus NG-11, launched in April 2019, the CryptIC box is a small unit shielded from the high radiation levels in space using a plastic coating.

However, while the coating protects the electronics from the worst of the radiation, it isn’t enough to stop interference with the microprocessors used to make encryption possible. ESA software product assurance engineer, Emmanuel Lesser, explains:

In orbit the problem has been that space radiation effects can compromise the key within computer memory causing ‘bit-flips’.

This is enough to disrupt communication as keys used on the ground and in space no longer match up.

The traditional solution to this is to use radiation-hardened equipment, but this is expensive.

Instead, the CryptIC is testing the feasibility of using microprocessor cores based around customisable, field-programmable gate arrays (FPGAs), which in effect offer redundancy should one core be affected by radiation.

If one core fails then another can step in, while the faulty core reloads its configuration, thereby repairing itself.

A second track is looking at using a backup key built into the CryptIC itself, which can’t be compromised from the ground.

The module also integrates a small ‘floating gate’ CERN-designed dosimeter which measures radiation levels. Meanwhile, the team is even testing different flash memory chips to see which performs the best.

The team will begin testing the module’s defence against encryption bit-flipping within weeks, after which it will be left to run for a year to make sure it’s reliable enough to be used on live missions.

Evidently, the project still has some proof-of-concept work ahead of it. But given the recent dramatic growth of low-cost satellites, it’s perhaps surprising that nobody had got around to solving this complex problem until now.