cryptix.tools

Class UnixCrypt

java.lang.Object

cryptix.tools.UnixCrypt

public class UnixCrypt
extends java.lang.Object

A Java-based implementation of the Unix crypt(3) function call, used for hashing user passwords in many Unix dialects.

Based on C source code written by Eric Young (eay@psych.uq.oz.au).

The crypt(3) algorithm is not recommended for new applications that require password hashing and do not need to be compatible with Unix, because it has the following weaknesses:

• Only the first 8 characters of the password are significant. The rest is silently truncated. This may mislead the user into thinking that an uncrackable password has been chosen, even though the first 8 characters may be crackable.
• Only the low 7 bits of the ASCII code of each character are used, which does not take advantage of additional entropy in non-US-ASCII passwords.
• The salt has a total of 12 significant bits. This is not enough to prevent a massive precomputation attack, where a dictionary of common passwords is hashed using all 4096 salts, after which individual passwords from the dictionary can be cracked quickly.
• The amount of computation needed is arguably not sufficient, taking into account improvements in processor speed since the algorithm was developed. A better approach would be to allow a variable number of iterations, with this number being stored with the salt.

Copyright © 1995-1997 Systemics Ltd on behalf of the Cryptix Development Team.
All rights reserved.

$Revision: 1.5 $

Since:

Cryptix 2.2.2

Author:

John F. Dumas (jdumas@zgs.com), Raif Naffah, David Hopwood

Constructor Summary

Constructors

Constructor and Description
UnixCrypt(java.lang.String salt) Constructs a UnixCrypt instance with the given salt value.

Method Summary

Modifier and Type	Method and Description
java.lang.String	crypt(java.lang.String original) Processes original and the salt value passed in the constructor using the crypt(3) algorithm, and returns the resulting hash as a String.
static void	main(java.lang.String[] args) Calculates the hash of a salt and password given on the command line.

Methods inherited from class java.lang.Object

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

Constructor Detail

UnixCrypt

public UnixCrypt(java.lang.String salt)

Constructs a UnixCrypt instance with the given salt value. If needed this value is appended with enough A's.

If salt is null then "AA" is taken as the salt value.

Parameters:

salt - the salt value as a String

Method Detail

crypt

public java.lang.String crypt(java.lang.String original)

Processes original and the salt value passed in the constructor using the crypt(3) algorithm, and returns the resulting hash as a String.

Parameters:

original - the plaintext password

Returns:

the hashed password

main

public static void main(java.lang.String[] args)

Calculates the hash of a salt and password given on the command line.

Usage:

    java cryptix.tools.UnixCrypt [<salt>] <clear-password>