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.