Random Number Generator Based on Metastabilities of Ring Oscillators and Irregular Sampling

This paper presents a new random number generator based on irregular sampling of regular waveform method. Wake-up uncertainty and shut-down metastabilities are used as additional entropy source to the timing jitter of the ring oscillators. To be able to change the stability of the rings, multiplexer and inverter are added to each ring. 34 ring oscillators are combined with an XOR gate to generate an irregular waveform that is used as the sampling clock. The select input of the multiplexers are controlled with a control unit. A signal that causes stability change with 2MHz frequency is routed from controller to the select inputs of the multiplexers and the XORed signal is masked with 2MHz, and 10ns width pulses. To reduce the speed of sampling, the irregular signal is downsampled that results in a final throughput of 13kbps. All of the circuits mentioned in this paper is implemented in Xilinx Zynq7000 FPGA. Furthermore, NIST 800-22 test suite is used to test the designed RNGs. Data sets of one million bits are collected with a UART module. All the NIST 800-22 test suite requirements are satisfied with the new proposed RNG.