Discussion on the Full Entropy Assumption of the SP 800-90 Series: NIST Interagency Report 8427

NIST Interagency Report (IR) 8427, Discussion on the Full Entropy Assumption of the SP 800-90 Series, is now available. This report supports the NIST Special Publication (SP) 800-90 series of publications.

The NIST SP 800-90 series provides guidance on the generation of high-quality random bits for cryptographic and non-cryptographic use. The security of a random number generator depends on the unpredictability of its outputs, which can be measured in terms of entropy. The NIST SP 800-90 series uses min-entropy to measure entropy. A full-entropy bitstring has an amount of entropy equal to its length. Full-entropy bitstrings are important for cryptographic applications because they have ideal randomness properties and may be used for any cryptographic purpose. Due to the difficulty of generating and testing full-entropy bitstrings, the NIST SP 800-90 series assumes that a bitstring has full entropy if the amount of entropy per bit is at least 1 - ε, where ε is at most 2^-32. NIST IR 8427 provides a justification for the selection of ε.