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/*  $Id: PBKDF2.java,v 1.1 2011/05/04 22:37:59 willuhn Exp $

    This file is part of CryptAlgs4Java
    Copyright (C) 2001-2010  Stefan Palme

    CryptAlgs4Java is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    CryptAlgs4Java is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

package org.kapott.cryptalgs;

import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

// TODO: implement some SPI interface?
public class PBKDF2
{
    public static byte[] deriveKey(byte[] salt, long nof_iterations, byte[] pass, int dkLen, String algname)
    {
        try {
            SecretKeySpec keyspec=new SecretKeySpec(pass,algname);
            Mac           mac=Mac.getInstance(algname);
            mac.init(keyspec);
            
            // see pkcs #5 v2.0 (RDH-2) bzw. pkcs #5 v2.1 (RDH-10)
            int    hLen=mac.getMacLength();
            byte[] dk=new byte[dkLen];
            
            int l=((dkLen-1)/hLen)+1;
            int r=dkLen - (l-1)*hLen;
            
            // System.out.println("deriveKey: hLen="+hLen+"; l="+l+"; r="+r);
            
            byte[] t=new byte[hLen];
            for (long i=0;i>24)&0xFF);
                u[salt.length+1]=(byte)(((i+1)>>16)&0xFF);
                u[salt.length+2]=(byte)(((i+1)>>8)&0xFF);
                u[salt.length+3]=(byte)(((i+1)>>0)&0xFF);
                
                for (int j=0;j>3)+1)<<3;
        byte   diff=(byte)(newlen-len);
        byte[] output=new byte[newlen];
        
        System.arraycopy(input,0, output,0, len);
        
        for (int i=len;i