Package com.sshtools.common.util

Class BCrypt

java.lang.Object
com.sshtools.common.util.BCrypt
public class BCrypt extends Object
BCrypt implements OpenBSD-style Blowfish password hashing using the scheme describes in "A Future-Adaptable Password Scheme" by Niels Provos and David Mazieres.

This password hashing system tries to thwart off-line password cracking using a computationally-intensive hashing algorithm, based on Bruce Schneier's Blowfish cipher. The work factor of the algorithm is parametised, so it can be increased as computers get faster.

Usage is really simple. To hash a password for the first time, call the hashpw method with a random salt, like this:

String pw_hash = BCrypt.hashpw(plain_password, BCrypt.gensalt());

To check whether a plaintext password matches one that has been hashed previously, use the checkpw method:

if (BCrypt.checkpw(candidate_password, stored_hash))
    System.out.println("It matches");
else
    System.out.println("It does not match");

The gensalt() method takes an optional parameter (log_rounds) that determines the computational complexity of the hashing:

String strong_salt = BCrypt.gensalt(10)
String stronger_salt = BCrypt.gensalt(12)

The amount of work increases exponentially (2**log_rounds), so each increment is twice as much work. The default log_rounds is 10, and the valid range is 4 to 31.

Version:
0.1
Author:
Damien Miller

  • Constructor Summary

    Constructors
    Constructor
    Description
    BCrypt()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    blf_dec(int[] data, int blocks)
     
    void
    blf_dec(int[] data, int offset, int blocks)
     
    void
    blf_enc(int[] data, int blocks)
     
    void
    blf_key(byte[] k)
     
    void
    blf_key(byte[] k, int len)
     
    static boolean
    checkpw(String plaintext, String hashed)
    Check that a plaintext password matches a previously hashed one
    static String
    gensalt()
    Generate a salt for use with the BCrypt.hashpw() method, selecting a reasonable default for the number of hashing rounds to apply
    static String
    gensalt(int log_rounds)
    Generate a salt for use with the BCrypt.hashpw() method
    static String
    hashpw(String password, String salt)
    Hash a password using the OpenBSD bcrypt scheme
    static void
    main(String[] args)
     
    static void
    report(int[] data, int len)
     

    Methods inherited from class java.lang.Object

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

  • Constructor Details

    • BCrypt

      public BCrypt()

  • Method Details

    • hashpw

      public static String hashpw(String password, String salt)
      Hash a password using the OpenBSD bcrypt scheme
      Parameters:
      password - the password to hash
      salt - the salt to hash with (perhaps generated using BCrypt.gensalt)
      Returns:
      the hashed password

    • gensalt

      public static String gensalt(int log_rounds)
      Generate a salt for use with the BCrypt.hashpw() method
      Parameters:
      log_rounds - the log2 of the number of rounds of hashing to apply - the work factor therefore increases as 2**log_rounds.
      Returns:
      an encoded salt value

    • gensalt

      public static String gensalt()
      Generate a salt for use with the BCrypt.hashpw() method, selecting a reasonable default for the number of hashing rounds to apply
      Returns:
      an encoded salt value

    • checkpw

      public static boolean checkpw(String plaintext, String hashed)
      Check that a plaintext password matches a previously hashed one
      Parameters:
      plaintext - the plaintext password to verify
      hashed - the previously-hashed password
      Returns:
      true if the passwords match, false otherwise

    • blf_enc

      public void blf_enc(int[] data, int blocks)

    • blf_dec

      public void blf_dec(int[] data, int blocks)

    • blf_dec

      public void blf_dec(int[] data, int offset, int blocks)

    • blf_key

      public void blf_key(byte[] k)

    • blf_key

      public void blf_key(byte[] k, int len)

    • report

      public static void report(int[] data, int len)

    • main

      public static void main(String[] args) throws Exception
      Throws:
      Exception