by Eric Montgomery
http://devewm.com/projects/pwdstrength
This utility aims to make it easy to determine and categorize the complexity of a password, hopefully simplifying writing validators for setting account passwords. By allowing or disallowing a password to be set based on its complexity alone, you remove the need for arbitrary restrictions like "must contain at least one upper-case letter and one number", "must contain at least one non-alphanumeric symbol", etc. This allows users to more freely choose passwords that fit their preferences while still enforcing some minimum level of security.
Password length also becomes less of an issue. For instance, the password "ئЖjΩ☮" has higher brute-force resistance than "aJ@2fz0z" while not actually satisfying the basic length requirement of passwords on most systems. Password Strength Meter classifies passwords based on their resistance to brute-force attack, allowing you to run only one check on a prospective password and allowing it if it meets the basic complexity level criteria you have specified.
Get an instance of the PasswordStrengthMeter class and then use the satisfiesStrengthClass method.
Example:
PasswordStrengthMeter passwordStrengthMeter = PasswordStrengthMeter.getInstance();
boolean passwordSecure = passwordStrengthMeter.satisfiesStrengthClass(
"pAssword123", PasswordStrengthClass.LENGTH_10_MIXED_CASE_WITH_NUMBER);
You can also get the number of iterations it would take to guess the given password. Example:
BigInteger result = passwordStrengthMeter.iterationCount("pAssword123");
(Note that the iteration count assumes a naive, sequential approach to password generation. A brute force password utility may generate its guesses more effectively, i.e. by using statistical models or dictionary word lists, and so may be able to reach the password more quickly than the result indicates.)
This is free and unencumbered software released into the public domain.
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