package gnu.crypto.hash;

// ----------------------------------------------------------------------------
// $Id: MD5.java,v 1.7 2005/10/06 04:24:14 rsdio Exp $
//
// Copyright (C) 2001, 2002, Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto 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, or (at your option)
// any later version.
//
// GNU Crypto 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; see the file COPYING.  If not, write to the
//
//    Free Software Foundation Inc.,
//    51 Franklin Street, Fifth Floor,
//    Boston, MA 02110-1301
//    USA
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library.  Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
//
// As a special exception, the copyright holders of this library give
// you permission to link this library with independent modules to
// produce an executable, regardless of the license terms of these
// independent modules, and to copy and distribute the resulting
// executable under terms of your choice, provided that you also meet,
// for each linked independent module, the terms and conditions of the
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// not derived from or based on this library.  If you modify this
// library, you may extend this exception to your version of the
// library, but you are not obligated to do so.  If you do not wish to
// do so, delete this exception statement from your version.
// ----------------------------------------------------------------------------

import gnu.crypto.Registry;
import gnu.crypto.util.Util;

/**
 * <p>The MD5 message-digest algorithm takes as input a message of arbitrary
 * length and produces as output a 128-bit "fingerprint" or "message digest" of
 * the input. It is conjectured that it is computationally infeasible to
 * produce two messages having the same message digest, or to produce any
 * message having a given prespecified target message digest.</p>
 *
 * <p>References:</p>
 *
 * <ol>
 *    <li>The <a href="http://www.ietf.org/rfc/rfc1321.txt">MD5</a> Message-
 *    Digest Algorithm.<br>
 *    R. Rivest.</li>
 * </ol>
 *
 * @version $Revision: 1.7 $
 */
public class MD5 extends BaseHash {

   // Constants and variables
   // -------------------------------------------------------------------------

   private static final int BLOCK_SIZE = 64; // inner block size in bytes

   private static final String DIGEST0 = "D41D8CD98F00B204E9800998ECF8427E";

   /** caches the result of the correctness test, once executed. */
   private static Boolean valid;

   /** 128-bit interim result. */
   private int h0, h1, h2, h3;

   // Constructor(s)
   // -------------------------------------------------------------------------

   /** Trivial 0-arguments constructor. */
   public MD5() {
      super(Registry.MD5_HASH, 16, BLOCK_SIZE);
   }

   /**
    * <p>Private constructor for cloning purposes.</p>
    *
    * @param md the instance to clone.
    */
   private MD5(MD5 md) {
      this();

      this.h0 = md.h0;
      this.h1 = md.h1;
      this.h2 = md.h2;
      this.h3 = md.h3;
      this.count = md.count;
      this.buffer = (byte[]) md.buffer.clone();
   }

   // Class methods
   // -------------------------------------------------------------------------

   // Instance methods
   // -------------------------------------------------------------------------

   // java.lang.Cloneable interface implementation ----------------------------

   public Object clone() {
      return new MD5(this);
   }

   // Implementation of concrete methods in BaseHash --------------------------

   protected synchronized void transform(byte[] in, int i) {
      int X0 =  (in[i++] & 0xFF) | (in[i++] & 0xFF) << 8 | (in[i++] & 0xFF) << 16 | in[i++] << 24;
      int X1 =  (in[i++] & 0xFF) | (in[i++] & 0xFF) << 8 | (in[i++] & 0xFF) << 16 | in[i++] << 24;
      int X2 =  (in[i++] & 0xFF) | (in[i++] & 0xFF) << 8 | (in[i++] & 0xFF) << 16 | in[i++] << 24;
      int X3 =  (in[i++] & 0xFF) | (in[i++] & 0xFF) << 8 | (in[i++] & 0xFF) << 16 | in[i++] << 24;
      int X4 =  (in[i++] & 0xFF) | (in[i++] & 0xFF) << 8 | (in[i++] & 0xFF) << 16 | in[i++] << 24;
      int X5 =  (in[i++] & 0xFF) | (in[i++] & 0xFF) << 8 | (in[i++] & 0xFF) << 16 | in[i++] << 24;
      int X6 =  (in[i++] & 0xFF) | (in[i++] & 0xFF) << 8 | (in[i++] & 0xFF) << 16 | in[i++] << 24;
      int X7 =  (in[i++] & 0xFF) | (in[i++] & 0xFF) << 8 | (in[i++] & 0xFF) << 16 | in[i++] << 24;
      int X8 =  (in[i++] & 0xFF) | (in[i++] & 0xFF) << 8 | (in[i++] & 0xFF) << 16 | in[i++] << 24;
      int X9 =  (in[i++] & 0xFF) | (in[i++] & 0xFF) << 8 | (in[i++] & 0xFF) << 16 | in[i++] << 24;
      int X10 = (in[i++] & 0xFF) | (in[i++] & 0xFF) << 8 | (in[i++] & 0xFF) << 16 | in[i++] << 24;
      int X11 = (in[i++] & 0xFF) | (in[i++] & 0xFF) << 8 | (in[i++] & 0xFF) << 16 | in[i++] << 24;
      int X12 = (in[i++] & 0xFF) | (in[i++] & 0xFF) << 8 | (in[i++] & 0xFF) << 16 | in[i++] << 24;
      int X13 = (in[i++] & 0xFF) | (in[i++] & 0xFF) << 8 | (in[i++] & 0xFF) << 16 | in[i++] << 24;
      int X14 = (in[i++] & 0xFF) | (in[i++] & 0xFF) << 8 | (in[i++] & 0xFF) << 16 | in[i++] << 24;
      int X15 = (in[i++] & 0xFF) | (in[i++] & 0xFF) << 8 | (in[i++] & 0xFF) << 16 | in[i  ] << 24;

      int A = h0;
      int B = h1;
      int C = h2;
      int D = h3;

      // hex constants are from md5.c in FSF Gnu Privacy Guard 0.9.2
      // round 1
      A += ((B & C) | (~B & D)) + X0 + 0xD76AA478;  A = B + (A << 7 | A >>> -7);
      D += ((A & B) | (~A & C)) + X1 + 0xE8C7B756;  D = A + (D << 12 | D >>> -12);
      C += ((D & A) | (~D & B)) + X2 + 0x242070DB;  C = D + (C << 17 | C >>> -17);
      B += ((C & D) | (~C & A)) + X3 + 0xC1BDCEEE;  B = C + (B << 22 | B >>> -22);

      A += ((B & C) | (~B & D)) + X4 + 0xF57C0FAF;  A = B + (A << 7 | A >>> -7);
      D += ((A & B) | (~A & C)) + X5 + 0x4787C62A;  D = A + (D << 12 | D >>> -12);
      C += ((D & A) | (~D & B)) + X6 + 0xA8304613;  C = D + (C << 17 | C >>> -17);
      B += ((C & D) | (~C & A)) + X7 + 0xFD469501;  B = C + (B << 22 | B >>> -22);

      A += ((B & C) | (~B & D)) + X8 + 0x698098D8;  A = B + (A << 7 | A >>> -7);
      D += ((A & B) | (~A & C)) + X9 + 0x8B44F7AF;  D = A + (D << 12 | D >>> -12);
      C += ((D & A) | (~D & B)) + X10 + 0xFFFF5BB1; C = D + (C << 17 | C >>> -17);
      B += ((C & D) | (~C & A)) + X11 + 0x895CD7BE; B = C + (B << 22 | B >>> -22);

      A += ((B & C) | (~B & D)) + X12 + 0x6B901122; A = B + (A << 7 | A >>> -7);
      D += ((A & B) | (~A & C)) + X13 + 0xFD987193; D = A + (D << 12 | D >>> -12);
      C += ((D & A) | (~D & B)) + X14 + 0xA679438E; C = D + (C << 17 | C >>> -17);
      B += ((C & D) | (~C & A)) + X15 + 0x49B40821; B = C + (B << 22 | B >>> -22);

      // round 2
      A += ((B & D) | (C & ~D)) + X1 + 0xF61E2562;  A = B + (A << 5 | A >>> -5);
      D += ((A & C) | (B & ~C)) + X6 + 0xC040B340;  D = A + (D << 9 | D >>> -9);
      C += ((D & B) | (A & ~B)) + X11 + 0x265E5A51; C = D + (C << 14 | C >>> -14);
      B += ((C & A) | (D & ~A)) + X0 + 0xE9B6C7AA;  B = C + (B << 20 | B >>> -20);

      A += ((B & D) | (C & ~D)) + X5 + 0xD62F105D;  A = B + (A << 5 | A >>> -5);
      D += ((A & C) | (B & ~C)) + X10 + 0x02441453; D = A + (D << 9 | D >>> -9);
      C += ((D & B) | (A & ~B)) + X15 + 0xD8A1E681; C = D + (C << 14 | C >>> -14);
      B += ((C & A) | (D & ~A)) + X4 + 0xE7D3FBC8;  B = C + (B << 20 | B >>> -20);

      A += ((B & D) | (C & ~D)) + X9 + 0x21E1CDE6;  A = B + (A << 5 | A >>> -5);
      D += ((A & C) | (B & ~C)) + X14 + 0xC33707D6; D = A + (D << 9 | D >>> -9);
      C += ((D & B) | (A & ~B)) + X3 + 0xF4D50D87;  C = D + (C << 14 | C >>> -14);
      B += ((C & A) | (D & ~A)) + X8 + 0x455A14ED;  B = C + (B << 20 | B >>> -20);

      A += ((B & D) | (C & ~D)) + X13 + 0xA9E3E905; A = B + (A << 5 | A >>> -5);
      D += ((A & C) | (B & ~C)) + X2 + 0xFCEFA3F8;  D = A + (D << 9 | D >>> -9);
      C += ((D & B) | (A & ~B)) + X7 + 0x676F02D9;  C = D + (C << 14 | C >>> -14);
      B += ((C & A) | (D & ~A)) + X12 + 0x8D2A4C8A; B = C + (B << 20 | B >>> -20);

      // round 3
      A += (B ^ C ^ D) + X5 + 0xFFFA3942;  A = B + (A << 4 | A >>> -4);
      D += (A ^ B ^ C) + X8 + 0x8771F681;  D = A + (D << 11 | D >>> -11);
      C += (D ^ A ^ B) + X11 + 0x6D9D6122; C = D + (C << 16 | C >>> -16);
      B += (C ^ D ^ A) + X14 + 0xFDE5380C; B = C + (B << 23 | B >>> -23);

      A += (B ^ C ^ D) + X1 + 0xA4BEEA44;  A = B + (A << 4 | A >>> -4);
      D += (A ^ B ^ C) + X4 + 0x4BDECFA9;  D = A + (D << 11 | D >>> -11);
      C += (D ^ A ^ B) + X7 + 0xF6BB4B60;  C = D + (C << 16 | C >>> -16);
      B += (C ^ D ^ A) + X10 + 0xBEBFBC70; B = C + (B << 23 | B >>> -23);

      A += (B ^ C ^ D) + X13 + 0x289B7EC6; A = B + (A << 4 | A >>> -4);
      D += (A ^ B ^ C) + X0 + 0xEAA127FA;  D = A + (D << 11 | D >>> -11);
      C += (D ^ A ^ B) + X3 + 0xD4EF3085;  C = D + (C << 16 | C >>> -16);
      B += (C ^ D ^ A) + X6 + 0x04881D05;  B = C + (B << 23 | B >>> -23);

      A += (B ^ C ^ D) + X9 + 0xD9D4D039;  A = B + (A << 4 | A >>> -4);
      D += (A ^ B ^ C) + X12 + 0xE6DB99E5; D = A + (D << 11 | D >>> -11);
      C += (D ^ A ^ B) + X15 + 0x1FA27CF8; C = D + (C << 16 | C >>> -16);
      B += (C ^ D ^ A) + X2 + 0xC4AC5665;  B = C + (B << 23 | B >>> -23);

      // round 4
      A += (C ^ (B | ~D)) + X0 + 0xF4292244;  A = B + (A << 6 | A >>> -6);
      D += (B ^ (A | ~C)) + X7 + 0x432AFF97;  D = A + (D << 10 | D >>> -10);
      C += (A ^ (D | ~B)) + X14 + 0xAB9423A7; C = D + (C << 15 | C >>> -15);
      B += (D ^ (C | ~A)) + X5 + 0xFC93A039;  B = C + (B << 21 | B >>> -21);

      A += (C ^ (B | ~D)) + X12 + 0x655B59C3; A = B + (A << 6 | A >>> -6);
      D += (B ^ (A | ~C)) + X3 + 0x8F0CCC92;  D = A + (D << 10 | D >>> -10);
      C += (A ^ (D | ~B)) + X10 + 0xFFEFF47D; C = D + (C << 15 | C >>> -15);
      B += (D ^ (C | ~A)) + X1 + 0x85845dd1;  B = C + (B << 21 | B >>> -21);

      A += (C ^ (B | ~D)) + X8 + 0x6FA87E4F;  A = B + (A << 6 | A >>> -6);
      D += (B ^ (A | ~C)) + X15 + 0xFE2CE6E0; D = A + (D << 10 | D >>> -10);
      C += (A ^ (D | ~B)) + X6 + 0xA3014314;  C = D + (C << 15 | C >>> -15);
      B += (D ^ (C | ~A)) + X13 + 0x4E0811A1; B = C + (B << 21 | B >>> -21);

      A += (C ^ (B | ~D)) + X4 + 0xF7537E82;  A = B + (A << 6 | A >>> -6);
      D += (B ^ (A | ~C)) + X11 + 0xBD3AF235; D = A + (D << 10 | D >>> -10);
      C += (A ^ (D | ~B)) + X2 + 0x2AD7D2BB;  C = D + (C << 15 | C >>> -15);
      B += (D ^ (C | ~A)) + X9 + 0xEB86D391;  B = C + (B << 21 | B >>> -21);

      h0 += A;
      h1 += B;
      h2 += C;
      h3 += D;
   }

   protected byte[] padBuffer() {
      int n = (int)(count % BLOCK_SIZE);
      int padding = (n < 56) ? (56 - n) : (120 - n);
      byte[] result = new byte[padding + 8];

      // padding is always binary 1 followed by binary 0s
      result[0] = (byte) 0x80;

      // save number of bits, casting the long to an array of 8 bytes
      long bits = count << 3;
      result[padding++] = (byte) bits;
      result[padding++] = (byte)(bits >>>  8);
      result[padding++] = (byte)(bits >>> 16);
      result[padding++] = (byte)(bits >>> 24);
      result[padding++] = (byte)(bits >>> 32);
      result[padding++] = (byte)(bits >>> 40);
      result[padding++] = (byte)(bits >>> 48);
      result[padding  ] = (byte)(bits >>> 56);

      return result;
   }

   protected byte[] getResult() {
      byte[] result = new byte[] {
         (byte) h0, (byte)(h0 >>> 8), (byte)(h0 >>> 16), (byte)(h0 >>> 24),
         (byte) h1, (byte)(h1 >>> 8), (byte)(h1 >>> 16), (byte)(h1 >>> 24),
         (byte) h2, (byte)(h2 >>> 8), (byte)(h2 >>> 16), (byte)(h2 >>> 24),
         (byte) h3, (byte)(h3 >>> 8), (byte)(h3 >>> 16), (byte)(h3 >>> 24)
      };

      return result;
   }

   protected void resetContext() {
      // magic MD5/RIPEMD128 initialisation constants
      h0 = 0x67452301;
      h1 = 0xEFCDAB89;
      h2 = 0x98BADCFE;
      h3 = 0x10325476;
   }

   public boolean selfTest() {
      if (valid == null) {
         valid = new Boolean(DIGEST0.equals(Util.toString(new MD5().digest())));
      }
      return valid.booleanValue();
   }
}
