Design of Ultra-High Throughput and Resource Efficiency TRNG Based on NAND-XOR and Feedback XOR Ring Oscillators

Recently, true random number generators (TRNGs) have received much attention from academia and industry. In this article, we propose a highly random and resource-efficient entropy source for TRNG. Two new ring oscillator (RO) structures, namely NAND-XOR RO (NXRO) and feedback-XOR RO (FXORRO), are designed as entropy sources for TRNG. The basic principle of the entropy sources is that all RO outputs are cross-XORed to generate random signals and also feedback to the FXORRO enable input, so as to randomly change the FXORRO oscillation state at high speed, thus significantly expanding the jitter and randomness. Moreover, the feedback random enable signals from NXRO outputs are used to initiate the FXORRO oscillation. The experiments on Xilinx Spartan-6 and Artix-7 FPGAs show that our TRNG based on the new entropy sources unit achieves throughputs of 400 Mbps and 600 Mbps while only consuming 12 Slices. The random bit sequence generated by this TRNG successfully passes the NIST SP 800-22, 800-90B, and AIS-31 tests without post-processing and outperforms existing FPGA-based TRNGs.