TRNGs

A true random number generator (TRNG) is a device that generates random numbers from physical processes that are inherently unpredictable. The randomness arises from fundamental physical phenomena rather than algorithmic processes. TRNGs are used when true entropy is required, such as cryptographic keys or security tokens; results are not guaranteed to be reproducible.

Common entropy sources include thermal noise in resistors, shot noise in diodes or transistors, radioactive decay, photon arrival times, and chaotic dynamics in nonlinear systems. Some TRNGs use quantum phenomena, such as photon counting or quantum phase noise. Many designs combine multiple sources and apply conditioning to produce statistically uniform bits.

Typical implementations capture the raw physical signal with sensors and digitize it, estimate the entropy, and apply post-processing or extraction to remove bias and correlations. Extraction uses hash functions, block ciphers in whitening modes, or dedicated randomness extractors. The resulting bitstream is intended to meet statistical randomness criteria.

Reliability and security: TRNGs can be sensitive to temperature, voltage, aging, and tampering, so devices incorporate health monitoring, calibration, and self-tests. Randomness is validated with statistical test suites and enterprise standards; outputs are often certified, and TRNGs are used to seed cryptographic pseudorandom number generators when required.

Applications and context: TRNGs are used to generate cryptographic keys, nonces, seeds for PRNGs, and in simulations where true randomness improves fidelity. They are contrasted with deterministic pseudorandom generators and are often integrated into security modules and cryptographic hardware.