“This Recommendation specifies the design principles and requirements for the entropy sources used by Random Bit Generators, and the tests for the validation of entropy sources. These entropy sources are intended to be combined with Deterministic Random Bit Generator mechanisms that are specified in SP 800-90A to construct Random Bit Generators, as specified in SP 800-90C…The NIST Special Publication (SP) 800-90 series of Recommendations provides  guidance on the construction and validation of Random Bit Generators (RBGs) in the form of Deterministic Random Bit Generators (DRBGs) or Non-deterministic Random Bit Generators (NRBGs) that can be used for cryptographic applications…”