Fully Digital Random Bit Generators for Cryptographic Applications

This paper is devoted to the analysis, implementation, and modeling of fully digital random bit generators based on recent research results on the design of stateless oscillator-based generators. A new approach to the data quality test is adopted where, instead of passing bunches of statistical tests on the raw data, the focus is on the verification of a minimum entropy limit for the delivered random numbers after the digital post-processing. The architecture of the proposed generator (noise source and post-processing algorithm) is described in detail and experimental results in a 90-nm CMOS process are reported. The fabricated device reaches a throughput of 1.74 Mb/s after post-processing with an area of 13000 mum² and a power consumption of about 240 muW when running at its maximum speed. A statistical model for the noise source is provided and the entropy of the post-processed data has been evaluated obtaining an entropy per byte higher than 7.999.