Package org.passay.entropy

Class ShannonEntropy

java.lang.Object
org.passay.entropy.ShannonEntropy
All Implemented Interfaces:
Entropy
public final class ShannonEntropy extends Object implements Entropy
Entropy bits estimate defined in NIST SP-800-63-1 User Selected Passwords.

See PDF Publication A1. "User Selected Passwords"

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private static final double
    FIRST_PHASE_BONUS
    Entropy bonus of the first phase.
    private static final int
    FIRST_PHASE_LENGTH
    Length of the first phase.
    private final boolean
    hasCompositionCheck
    Whether at least 1 uppercase and special/symbol character is enforced.
    private final boolean
    hasDictionaryCheck
    Whether a dictionary was used to check the password.
    private final int
    passwordSize
    Size of the password.
    private static final double
    SECOND_PHASE_BONUS
    Entropy bonus of the second phase.
    private static final int
    SECOND_PHASE_LENGTH
    Length of the second phase.
    private static final int[]
    SHANNON_COMPOSITION_SIEVE
    Array used for determining composition "bonus" for calculating the Shannon entropy estimate.
    private static final int[]
    SHANNON_DICTIONARY_SIEVE
    Array used for determining dictionary entropy "bonus" for calculating the Shannon entropy estimate.
    private static final double
    THIRD_PHASE_BONUS
    Entropy bonus of the third phase.
    private static final int
    THIRD_PHASE_LENGTH
    Length of the second phase.

  • Constructor Summary

    Constructors
    Constructor
    Description
    ShannonEntropy(boolean dictionaryCheck, boolean compositionCheck, int pwordSize)
    Creates a new shannon entropy estimate.

  • Method Summary

    Modifier and Type
    Method
    Description
    double
    estimate()
    Returns the entropy bits of a user selected password.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • FIRST_PHASE_LENGTH

      private static final int FIRST_PHASE_LENGTH
      Length of the first phase.
      See Also:

    • SECOND_PHASE_LENGTH

      private static final int SECOND_PHASE_LENGTH
      Length of the second phase.
      See Also:

    • THIRD_PHASE_LENGTH

      private static final int THIRD_PHASE_LENGTH
      Length of the second phase.
      See Also:

    • FIRST_PHASE_BONUS

      private static final double FIRST_PHASE_BONUS
      Entropy bonus of the first phase.
      See Also:

    • SECOND_PHASE_BONUS

      private static final double SECOND_PHASE_BONUS
      Entropy bonus of the second phase.
      See Also:

    • THIRD_PHASE_BONUS

      private static final double THIRD_PHASE_BONUS
      Entropy bonus of the third phase.
      See Also:

    • SHANNON_DICTIONARY_SIEVE

      private static final int[] SHANNON_DICTIONARY_SIEVE
      Array used for determining dictionary entropy "bonus" for calculating the Shannon entropy estimate.

    • SHANNON_COMPOSITION_SIEVE

      private static final int[] SHANNON_COMPOSITION_SIEVE
      Array used for determining composition "bonus" for calculating the Shannon entropy estimate.

    • hasDictionaryCheck

      private final boolean hasDictionaryCheck
      Whether a dictionary was used to check the password.

    • hasCompositionCheck

      private final boolean hasCompositionCheck
      Whether at least 1 uppercase and special/symbol character is enforced.

    • passwordSize

      private final int passwordSize
      Size of the password.

  • Constructor Details

    • ShannonEntropy

      public ShannonEntropy(boolean dictionaryCheck, boolean compositionCheck, int pwordSize)
      Creates a new shannon entropy estimate.
      Parameters:
      dictionaryCheck - whether or not a common passwords dictionary is checked against the password (50,000 dictionary words are recommended)
      compositionCheck - whether at least 1 uppercase and special/symbol character is enforced (not using common substitutions such as s to $ are recommended)
      pwordSize - size of the password

  • Method Details

    • estimate

      public double estimate()
      Returns the entropy bits of a user selected password. This estimate is based on a 94 Character Alphabet and is a "ballpark" estimate based on Claude Shannon's observations.

      See PDF Publication A1. "User Selected Passwords"

      Specified by:
      estimate in interface Entropy
      Returns:
      estimated entropy bits given password properties