This International Standard specifies a conceptual model for a random bit generator for cryptographic purposes, together with the elements of this model. This International Standard also includes the following: • the description of the main elements required for a non-deterministic random bit generator; • the description of the main elements required for a deterministic random bit generator; • their characteristics; • their security requirements. Where there is a requirement to produce sequences of random numbers from random bit strings, Annex B provides guidance on how this can be performed. Techniques for statistical testing of random bit generators for the purposes of independent verification or validation, and detailed designs for such generators, are outside the scope of this International Standard.