TRNG based on the coherent sampling
Résumé
We propose an efficient randomness extraction method based on the coherent sampling - a mutual sampling of two close-frequency jittery clock signals. We extend in many ways the concept proposed by P. Kohlbrenner and K. Gaj at ACM/SIGDA FPGA 2004 symposium. Thanks to the changed structure, we obtain fast random bit-streams that pass the FIPS and NIST test suites without post-processing. Moreover, the proposed implementation does not need manual intervention on the placement and routing level. The principle have been successfully implemented in two different FPGA families (Xilinx and Actel) up to now and it can be extended to any FPGA family or ASIC. The generator needs very small logic resources and the output bit-rate reaches 3Mbits/s. Because of its simplicity, it can be easily characterized by a mathematical (stochastic) model (see the presentation of F. Bernard and V. Fischer).