A hybrid entropy source scheme for true random number generator

True random number generators (TRNGs) are gaining increasing attention as essential components in information security systems. In this paper, a dual-path reconfigurable ring (DPRR) that generates both jitter and metastability is proposed. Its fundamental unit consists of seven XOR gates and two 2-to-1 multiplexers (MUXs). The advantage of this method lies in utilizing the ability of XOR gates to quickly accumulate jitter and the characteristic of the 2-to-1 MUX to switch the loop path, simultaneously inducing jitter and instability in the proposed scheme. The DPRR-based TRNG was deployed on the Field Programmable Gate Array (FPGA) platforms with Artix-7 and Kintex-7 using automatic layout and routing mode, which consumed 33 Look-up Tables (LUTs) and 12 D Flip-Flops (DFFs) to achieve 200/300 Mbps throughput. Experimental results demonstrate that the random sequences generated by this TRNG pass the NIST SP800-22, NIST SP800-90B, AIS-31, and robustness test without requiring post-processing circuits.