Random Number Generation Based on Oscillatory Metastability in Ring Circuits

Random number generator designs are discussed, which utilize oscillatory metastability, induced by switching between two stable states of ring-connected digital gates. For a short time after the switch-over the circuits behave quite randomly, influenced by the circuit noise. The authors provide simple programs, which simulate the fundamental behavior of their circuits. They also present a mathematical model and theoretical explanations of the underlying physical phenomena, the random phase drift and pulse decay. These also illuminate the principles of other recently published random number generators. The feasibility of the designs was confirmed by FPGA prototypes. These random number generators are small, fast and built of standard logic gates. The simplest example contains just one XOR gate as the source of randomness.