A Proposal of an Embedded On-the-fly Filter for a Circuit-based Random Number Generator

Physical random numbers are widely regarded as unpredictable. However, their bit distribution does not always follow the ideal uniformity. Therefore, when using physical random numbers in encryption, it is essential to have sufficient unpredictability.In this paper, we designed a circuit that integrates a filtering process into a ring oscillator-type random number generator and then evaluated the effect of this integration on the entropy. This filtering process eliminates the output of the random number generator that exhibits statistically biased characteristics. We used the Non-IID test of NIST SP 800-90B to evaluate the filtering process. The result of this evaluation indicates that while the filtering enhances the entropy in several instances, it also leads to loss of stability or a decrease in some entropy. In subsequent experiments, we will collect additional data and meticulously examine the relationship between filtering and entropy.