Analysis and Enhancement of Random Number Generator in FPGA Based on Oscillator Rings

摘要

A true random number generator (TRNG) is an importantcomponent in cryptographic systems. Designing a fastand secure TRNG in an FPGA is a challenging task. In thispaper, we analyze the TRNG designed by Sunar et al. (2007)based on XOR of the outputs of several oscillator rings. Wepropose an enhanced TRNG with better randomness characteristicsthat does not require postprocessing and passesthe statistical tests. We have shown by experiment that thefrequencies of the equal length oscillator rings in the TRNGare not identical. The difference is due to the placement ofthe inverters in the FPGA and the resulting routing betweenthe inverters. We have implemented our proposed TRNG inan Altera Cyclone II FPGA. Our implementation has passedthe NIST and DIEHARD statistical tests with a throughputof 100 Mbps and with a usage of less than 100 logic elementsin the FPGA. The restart experiments have shownthat the output from our TRNG behaves truly random andnot pseudorandom.