NIST has released the initial public draft of NIST Interagency Report (IR) 8427, which discusses the full entropy assumption in the SP 800-90 series of publications. The SP 800-90 series is used to generate high-quality random bits for cryptographic and non-cryptographic applications. The security of random number generators depends on the unpredictability of their outputs, which can be measured in terms of entropy. The NIST SP 800-90 series uses min-entropy to measure entropy, and a full-entropy bitstring has an amount of entropy equal to its length. However, due to the difficulty of generating and testing full-entropy bitstrings, the 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. The public comment period for NIST IR 8427 is open through October 31, 2022, and the public is encouraged to review and comment on the document to ensure that the standards are accurate and effective.
Keywords: entropy, bitstring, randomness
