Entropy

{
  "id": "MLC-T-CYB-001572",
  "term": "Entropy",
  "field": "Cybersecurity",
  "definition": "1. A measure of the randomness or uncertainty of a random variable.\n\n2. The amount of uncertainty that an attacker faces to determine the value of a secret. Entropy is usually stated in bits. A value with n bits of entropy has the same degree of uncertainty as a uniformly distributed n-bit random value.\n\n3. The entropy of a random variable X is a mathematical measure of the expected amount of information provided by an observation of X. As such, entropy is always relative to an observer and his or her knowledge prior to an observation.\n\n4. A measure of the disorder or randomness in a closed system. The entropy of uncertainty of a random variable X with probabilities pi, …, pn is defined to be H(X)=-∑_(i=1)^n 〖p_i log〖 p〗_i 〗\n\n5. A measure of the amount of uncertainty an attacker faces to determine the value of a secret. Entropy is usually stated in bits. A value havingnbits of entropy has the same degree of uncertainty as a uniformly distributedn-bit random value.\n\n6. A measure of the disorder, randomness or variability in a closed system. Min-entropy is the measure used in this Recommendation.\n\n7. A measure of the disorder, randomness or variability in a closed system. See SP 800-90B.\n\n8. A measure of the amount of uncertainty an attacker faces to determine the value of a secret. Entropy is usually stated in bits. A value having n bits of entropy has the same degree of uncertainty as a uniformly distributed n-bit random value.\n\n9. A measure of the disorder, randomness, or variability in a closed system; see SP 800-90B.\n\n10. A measure of the amount of uncertainty that an Attacker faces to determine the value of a secret. Entropy is usually stated in bits. See Appendix A.",
  "references": [
    "NIST IR 8427",
    "NIST SP 800-63-4; NIST SP 800-63A-4",
    "NIST SP 800-133 [Superseded]",
    "NIST SP 800-22 Rev. 1a",
    "NIST SP 800-63-3 [Superseded]",
    "NIST SP 800-90A Rev. 1; NIST SP 800-90B",
    "NIST SP 800-133 Rev.1 [Superseded]",
    "NIST SP 800-133 Rev. 2",
    "NIST SP 800-63-2 [Superseded]",
    "NIST CSRC Glossary"
  ],
  "url": "https://mlchart.com/terminology/cybersecurity/entropy/"
}