- Pseudo-random number generator (PRNG): uses algorithms to produce random results, often from short randomization seeds. Their generators are capable of high throughputs, but attackers can derive the random number from knowledge of the seed.
- Hardware/true random number generator (TRNG): measures a physical phenomenon expected to be random. Even though it can deliver high quality random, the rate is usually limited, resulting in entropy starvation that will impact performance, security, or both.
- Hybrid random number generator: uses both hardware and software derived randomness depending on the read rate needed and has similar qualities to the PRNG at high throughputs.
- Quantum random number generators (QRNG): measure true random directly from a quantum effect. It delivers full entropy and can do so at very high throughput. No seed is needed. QuintessenceLabs QRNG, qStream, delivers 100% entropy at 1 Gbit/s.
