Multi-bit per cycle true random number generator based on XOR-XNOR ring oscillator unit

Abstract

To achieve a fast and resource-efficient entropy source, we present a novel oscillator unit, called XOR-XNOR ring oscillator (XXRO) which consists of an XOR gate and an XNOR gate. The XXRO unit has an internal feedback loop that allows the accumulation of jitter within the unit. Connecting multiple XXRO units forms a new entropy source. We utilize the differences between the XXRO units in the entropy sources to output two bits pre cycle, increasing the throughput of the True Random Number Generator (TRNG) while optimizing the use of hardware resources. In this paper, we use four proposed entropy source to form a TRNG, by sampling the two outputs of each entropy source individually and performing an XOR computation based on the corresponding positions to obtain random numbers. Experimental results indicate that when working at a throughput of 250 Mbps under a 125 MHz sampling clock, both outputs of the proposed TRNG pass the randomness tests and other performance tests.