Evaluation of a couple of true random number generators with liberally licensed hardware, firmware, and drivers

Sequences of high quality random bits are required in virtually all modern security and cryptography applications, pushing designers to devise hardware-based true random number generators (TRNGs). Alongside architectures made by big players of information technology and/or proposed via peer reviewed channels, many alternatives exist. The recent, powerful trend to interconnect even humble devices creates a significant deployment space for some of them, thanks to properties such as low-cost, good suitability to augment existing hardware, and readily available hardware/firmware/driver designs with liberal licenses. Consequently, there is practical relevance in a formal evaluation of their design. In this work, the "InfNoise" and "Redoubler" open architectures are investigated, finding them to belong to the chaos-based TRNG class and to bear similarity to some academic designs from the late'90s. Despite some some margins for improvement, the designs are found to admit formal justification.