Spoof-proof random number generator • The Register

Scientists in the US have built a system for creating truly random numbers which cannot be tampered with by a third party.

Random numbers might be needed to pick jury members out of a field without bias, or provide security algorithms. Quantum events offer the promise of true randomness. Meanwhile, a phenomenon called quantum entanglement, which determines that two quantum particles emitted at the same time can remain forever linked in their state, no matter how far apart they are, allows for boffins to check their work.

While entanglement offers a way of checking a truly random source of data, such systems can potentially be spoofed if a rogue actor secretly mistimes one of the measurements.

A paper published in Nature by University of Colorado, Boulder, postdoctoral student Gautam Kavuri and colleagues, describes a new system which provides a publicly available hash chain, greatly raising the difficulty of tampering with the record of the timing of quantum measurements. The record of measurements is also available online.

In an accompanying article, Peter Brown, associate professor at France’s Institut Polytechnique de Paris, said: “Kavuri and colleagues combine the high security of quantum random-number generation with a classical protocol that ensures not only that the output is truly random, but also that the randomness can be verified.”

The Colorado University Randomness Beacon (CURBy) relies on two entangled photons measured at two sites at the same time, 110 meters apart. The sequence of measurement is recorded publicly on a hash chain, which allows observers to detect any attempt to tamper with it. The research team generated random numbers 7,454 times in 40 days and found that a truly random number was generated 7,434 times, which they call a 99.7 percent success rate.

Brown noted that for a bad actor to control the final output of the random-number generator undetected, the records of the entanglement measurements and all the hash chains would need to be compromised across the experiment’s disparate geographical locations. “Compared with previous results, the difficulty of attacking the system undetected is substantially increased,” he said.

Brown continued: “The use of traceable quantum randomness to prevent corruption and distribute resources could strengthen the public’s trust in these systems. In the current era of misinformation, at least we will be able to trust in randomness.” ®