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The following publications specify the design and implementation of random bit generators (RBGs), in two classes: Deterministic Random Bit Generators (pseudo RBGs); and Non-Deterministic Random bit Generators (True RBGs).
On May 2-3, 2016, NIST hosted a workshop on Random Number Generation to discuss the SP 800-90 series of documents--specifically, SP 800-90B and SP 800-90C.
NIST is implementing a source of public randomness--the NIST Randomness Beacon. The service (at https://beacon.nist.gov/home) uses two independent commercially available sources of randomness, each with an independent hardware entropy source and SP 800-90-approved components.
The Beacon is designed to provide unpredictability, autonomy, and consistency. Unpredictability means that users cannot algorithmically predict bits before they are made available by the source. Autonomy means that the source is resistant to attempts by outside parties to alter the distribution of the random bits. Consistency means that a set of users can access the source in such a way that they are confident they all receive the same random string.