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For the purposes of this Recommendation, an n-bit string is said to provide full entropy if the string is obtained through a process that is estimated to have at least (1−ε)n bits of entropy, where 0 ≤ ε ≤ 2-64.
NIST SP 800-133 under Full entropy
For the purposes of this Recommendation, a source of full-entropy bitstrings serves as a practical approximation to a source of ideal random bitstrings of the same length (see ideal random sequence).
NIST SP 800-90A Rev. 1 under Full Entropy