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 - specifies the characteristics of the main elements required for a non-deterministic random bit generator, - specifies the characteristics of the main elements required for a deterministic random bit generator, - establishes the security requirements for both the non-deterministic and the deterministic random bit generator. Where there is a requirement to produce sequences of random numbers from random bit strings, Annex B gives guidelines 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.