A High Throughput True Random Number Generator using Metastability and Chaos

Abstract

A True Random Number Generator based on a differential ring oscillator with two different signal paths, that uses two different entropy sources, i.e., metastability and chaos, is presented. The ring oscillator is made from a differential delay cell that uses two transmission gates along with a base transistor to pull itself into the metastable mode. When the delay cell leaves the metastable mode and enters the oscillation mode, the circuit’s noise causes its initial phase to be random, acting as the first entropy source. During the oscillation mode, the ring oscillator’s frequency is controlled using the output of a chaotic circuit, which acts as the second entropy source. For the said purpose, the delay cell has two differential pairs for input, which allows the oscillator to have two signal paths with different delays. A 3/5 cell ring oscillator was designed and simulated in a 65nm CMOS process. The proposed TRNG passes all 15 of the NIST’s statistical tests without post-processing while generating random numbers up to 4 Gbps with a power consumption of 10.4 mW and efficiency of 2.575 pJ/bit.