The National Institute of Standards and Technology (NIST), in collaboration with the University of Colorado Boulder, has developed the Colorado University Randomness Beacon (CURBy)—a groundbreaking quantum random number generator that produces verifiably true randomness using quantum entanglement. Unlike classical pseudo-random number generators, CURBy leverages quantum mechanics to create fundamentally unpredictable outputs.
The Challenge of Classical Randomness
Traditional random number generators rely on algorithms or physical processes (like dice rolls) that are inherently predictable or manipulable. Classical algorithms indeed produce only pseudo-random numbers, which are deterministic sequences that can be reverse-engineered with sufficient knowledge of the system. This vulnerability stems from their algorithmic nature, where outputs are generated through mathematical operations rather than inherent randomness.
Mechanism of Pseudorandom Number Generators (PRNGs)
PRNGs use a deterministic algorithm and an initial “seed” value to produce sequences of numbers that mimic randomness. Common methods include Linear Congruential Generators (LCGs) which can generate numbers via the recurrence relation X_{n+1} = (aX_n + c) \mod m, where (multiplier), (increment), and (modulus) are fixed parameters. Another common method is Middle-square or Lagged Fibonacci methods but they also rely on iterative mathematical operations. Since the process is entirely algorithmic, the same seed always produces identical sequences.
Reverse-Engineering Vulnerabilities
PRNG outputs can be reverse-engineered. Given three successive outputs () from an LCG, the parameters and can be deduced by solving linear equations derived from the recurrence. If the seed is compromised, the entire sequence becomes predictable. Simpler PRNGs (e.g., untruncated LCGs) are particularly susceptible, as their linear structure allows full state recovery from minimal outputs.
This determinism contrasts sharply with true random number generators (TRNGs), which derive unpredictability from physical phenomena (e.g., thermal noise) and cannot be reverse-engineered.
Quantum Solution: Entangled Photons
CURBy harnesses quantum entanglement to generate true randomness. A nonlinear crystal generates pairs of entangled photons, which travel via optical fiber to separate labs. Each photon’s polarization is measured upon arrival. Due to quantum nonlocality, these measurements produce intrinsically random outcomes that cannot be predicted, even with complete knowledge of the system. The process repeats 250,000 times per second, converting raw data into 512-bit binary strings.
CURBy Performance and Reliability
In its initial 40-day operational phase: CURBy successfully generated random numbers in 7,434 out of 7,454 attempts (99.7% success rate). The system operates continuously, providing a publicly accessible stream of certified randomness.
Applications and Impact
CURBy enables true randomness strengthens encryption keys against quantum and classical attacks. It supports unbiased jury selection, resource lotteries, and auditing processes and it ffers a gold standard for simulations, statistical sampling, and blockchain technologies.
CURBy marks a pivotal shift toward quantum-secured infrastructure, combining theoretical rigor with practical, real-world deployment.
