org.passay.entropy

Class ShannonEntropy

java.lang.Object

org.passay.entropy.ShannonEntropy

All Implemented Interfaces:

Entropy

public 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"

Author:

Middleware Services

Field Summary

Fields

Modifier and Type	Field and Description
static double	FIRST_PHASE_BONUS Entropy bonus of the first phase.
static int	FIRST_PHASE_LENGTH Length of the first phase.
static double	SECOND_PHASE_BONUS Entropy bonus of the second phase.
static int	SECOND_PHASE_LENGTH Length of the second phase.
static int[]	SHANNON_COMPOSITION_SIEVE Array used for determining composition "bonus" for calculating the Shannon entropy estimate.
static int[]	SHANNON_DICTIONARY_SIEVE Array used for determining dictionary entropy "bonus" for calculating the Shannon entropy estimate.
static double	THIRD_PHASE_BONUS Entropy bonus of the third phase.
static int	THIRD_PHASE_LENGTH Length of the second phase.

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and 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 Detail

FIRST_PHASE_LENGTH

public static final int FIRST_PHASE_LENGTH

Length of the first phase.

See Also:

Constant Field Values

SECOND_PHASE_LENGTH

public static final int SECOND_PHASE_LENGTH

Length of the second phase.

See Also:

Constant Field Values

THIRD_PHASE_LENGTH

public static final int THIRD_PHASE_LENGTH

Length of the second phase.

See Also:

Constant Field Values

FIRST_PHASE_BONUS

public static final double FIRST_PHASE_BONUS

Entropy bonus of the first phase.

See Also:

Constant Field Values

SECOND_PHASE_BONUS

public static final double SECOND_PHASE_BONUS

Entropy bonus of the second phase.

See Also:

Constant Field Values

THIRD_PHASE_BONUS

public static final double THIRD_PHASE_BONUS

Entropy bonus of the third phase.

See Also:

Constant Field Values

SHANNON_DICTIONARY_SIEVE

public static final int[] SHANNON_DICTIONARY_SIEVE

Array used for determining dictionary entropy "bonus" for calculating the Shannon entropy estimate.

SHANNON_COMPOSITION_SIEVE

public static final int[] SHANNON_COMPOSITION_SIEVE

Array used for determining composition "bonus" for calculating the Shannon entropy estimate.

Constructor Detail

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 or not 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 Detail

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