package gnu.crypto.key.srp6;

// ----------------------------------------------------------------------------
// $Id: SRPKeyPairRawCodec.java,v 1.2 2005/10/06 04:24:16 rsdio Exp $
//
// Copyright (C) 2003 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
// license of that module.  An independent module is a module which is
// 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.key.IKeyPairCodec;

import java.io.ByteArrayOutputStream;
import java.math.BigInteger;
import java.security.PrivateKey;
import java.security.PublicKey;

/**
 * <p>An object that implements the {@link IKeyPairCodec} operations for the
 * <i>Raw</i> format to use with SRP keypairs.</p>
 *
 * <p>Reference:</p>
 * <ol>
 *    <li><a href="http://srp.stanford.edu/design.html">SRP Protocol Design</a><br>
 *    Thomas J. Wu.</li>
 * </ol>
 *
 * @version $Revision: 1.2 $
 */
public class SRPKeyPairRawCodec implements IKeyPairCodec {

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

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

   // implicit 0-arguments constructor

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

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

   // gnu.crypto.keys.IKeyPairCodec interface implementation ------------------

   public int getFormatID() {
      return RAW_FORMAT;
   }

   /**
    * <p>Returns the encoded form of the designated SRP public key according to
    * the <i>Raw</i> format supported by this library.</p>
    *
    * <p>The <i>Raw</i> format for an SRP public key, in this implementation, is
    * a byte sequence consisting of the following:</p>
    * <ol>
    *    <li>4-byte magic consisting of the value of the literal
    *    {@link Registry#MAGIC_RAW_SRP_PUBLIC_KEY},<li>
    *    <li>1-byte version consisting of the constant: 0x01,</li>
    *    <li>4-byte count of following bytes representing the SRP parameter
    *    <code>N</code> in internet order,</li>
    *    <li>n-bytes representation of a {@link BigInteger} obtained by invoking
    *    the <code>toByteArray()</code> method on the SRP parameter
    *    <code>N</code>,</li>
    *    <li>4-byte count of following bytes representing the SRP parameter
    *    <code>g</code>,</li>
    *    <li>n-bytes representation of a {@link BigInteger} obtained by invoking
    *    the <code>toByteArray()</code> method on the SRP parameter
    *    <code>g</code>,</li>
    *    <li>4-byte count of following bytes representing the SRP parameter
    *    <code>y</code>,</li>
    *    <li>n-bytes representation of a {@link BigInteger} obtained by invoking
    *    the <code>toByteArray()</code> method on the SRP parameter
    *    <code>y</code>,</li>
    * </ol>
    *
    * @param key the key to encode.
    * @return the <i>Raw</i> format encoding of the designated key.
    * @throws IllegalArgumentException if the designated key is not an SRP one.
    */
   public byte[] encodePublicKey(PublicKey key) {
      if (!(key instanceof SRPPublicKey)) {
         throw new IllegalArgumentException("key");
      }

      SRPPublicKey srpKey = (SRPPublicKey) key;
      ByteArrayOutputStream baos = new ByteArrayOutputStream();

      // magic
      baos.write(Registry.MAGIC_RAW_SRP_PUBLIC_KEY[0]);
      baos.write(Registry.MAGIC_RAW_SRP_PUBLIC_KEY[1]);
      baos.write(Registry.MAGIC_RAW_SRP_PUBLIC_KEY[2]);
      baos.write(Registry.MAGIC_RAW_SRP_PUBLIC_KEY[3]);

      // version
      baos.write(0x01);

      // N
      byte[] buffer = srpKey.getN().toByteArray();
      int length = buffer.length;
      baos.write( length >>> 24        );
      baos.write((length >>> 16) & 0xFF);
      baos.write((length >>>  8) & 0xFF);
      baos.write( length         & 0xFF);
      baos.write(buffer, 0, length);

      // g
      buffer = srpKey.getG().toByteArray();
      length = buffer.length;
      baos.write( length >>> 24        );
      baos.write((length >>> 16) & 0xFF);
      baos.write((length >>>  8) & 0xFF);
      baos.write( length         & 0xFF);
      baos.write(buffer, 0, length);

      // y
      buffer = srpKey.getY().toByteArray();
      length = buffer.length;
      baos.write( length >>> 24        );
      baos.write((length >>> 16) & 0xFF);
      baos.write((length >>>  8) & 0xFF);
      baos.write( length         & 0xFF);
      baos.write(buffer, 0, length);

      return baos.toByteArray();
   }

   public PublicKey decodePublicKey(byte[] k) {
      // magic
      if (k[0] != Registry.MAGIC_RAW_SRP_PUBLIC_KEY[0]
            || k[1] != Registry.MAGIC_RAW_SRP_PUBLIC_KEY[1]
            || k[2] != Registry.MAGIC_RAW_SRP_PUBLIC_KEY[2]
            || k[3] != Registry.MAGIC_RAW_SRP_PUBLIC_KEY[3]) {
         throw new IllegalArgumentException("magic");
      }

      // version
      if (k[4] != 0x01) {
         throw new IllegalArgumentException("version");
      }
      int i = 5;

      int l;
      byte[] buffer;

      // N
      l = k[i++] << 24 | (k[i++] & 0xFF) << 16 | (k[i++] & 0xFF) << 8 | (k[i++] & 0xFF);
      buffer = new byte[l];
      System.arraycopy(k, i, buffer, 0, l);
      i += l;
      BigInteger N = new BigInteger(1, buffer);

      // g
      l = k[i++] << 24 | (k[i++] & 0xFF) << 16 | (k[i++] & 0xFF) << 8 | (k[i++] & 0xFF);
      buffer = new byte[l];
      System.arraycopy(k, i, buffer, 0, l);
      i += l;
      BigInteger g = new BigInteger(1, buffer);

      // y
      l = k[i++] << 24 | (k[i++] & 0xFF) << 16 | (k[i++] & 0xFF) << 8 | (k[i++] & 0xFF);
      buffer = new byte[l];
      System.arraycopy(k, i, buffer, 0, l);
      i += l;
      BigInteger y = new BigInteger(1, buffer);

      return new SRPPublicKey(N, g, y);
   }

   /**
    * <p>Returns the encoded form of the designated SRP private key according to
    * the <i>Raw</i> format supported by this library.</p>
    *
    * <p>The <i>Raw</i> format for an SRP private key, in this implementation,
    * is a byte sequence consisting of the following:</p>
    * <ol>
    *    <li>4-byte magic consisting of the value of the literal
    *    {@link Registry#MAGIC_RAW_SRP_PRIVATE_KEY},<li>
    *    <li>1-byte version consisting of the constant: 0x01,</li>
    *    <li>4-byte count of following bytes representing the SRP parameter
    *    <code>N</code> in internet order,</li>
    *    <li>n-bytes representation of a {@link BigInteger} obtained by invoking
    *    the <code>toByteArray()</code> method on the SRP parameter
    *    <code>N</code>,</li>
    *    <li>4-byte count of following bytes representing the SRP parameter
    *    <code>g</code>,</li>
    *    <li>n-bytes representation of a {@link BigInteger} obtained by invoking
    *    the <code>toByteArray()</code> method on the SRP parameter
    *    <code>g</code>,</li>
    *    <li>4-byte count of following bytes representing the SRP parameter
    *    <code>x</code>,</li>
    *    <li>n-bytes representation of a {@link BigInteger} obtained by invoking
    *    the <code>toByteArray()</code> method on the SRP parameter
    *    <code>x</code>,</li>
    *    <li>one byte which indicates whether the SRP parameter <code>v</code>
    *    is included in this encoding (value <code>0x01</code>) or not
    *    (value <code>0x00</code>).</li>
    *    <li>4-byte count of following bytes representing the SRP parameter
    *    <code>v</code>,</li>
    *    <li>n-bytes representation of a {@link BigInteger} obtained by invoking
    *    the <code>toByteArray()</code> method on the SRP parameter
    *    <code>v</code>,</li>
    * </ol>
    *
    * @param key the key to encode.
    * @return the <i>Raw</i> format encoding of the designated key.
    * @throws IllegalArgumentException if the designated key is not an SRP one.
    */
   public byte[] encodePrivateKey(PrivateKey key) {
      if (!(key instanceof SRPPrivateKey)) {
         throw new IllegalArgumentException("key");
      }

      SRPPrivateKey srpKey = (SRPPrivateKey) key;
      ByteArrayOutputStream baos = new ByteArrayOutputStream();

      // magic
      baos.write(Registry.MAGIC_RAW_SRP_PRIVATE_KEY[0]);
      baos.write(Registry.MAGIC_RAW_SRP_PRIVATE_KEY[1]);
      baos.write(Registry.MAGIC_RAW_SRP_PRIVATE_KEY[2]);
      baos.write(Registry.MAGIC_RAW_SRP_PRIVATE_KEY[3]);

      // version
      baos.write(0x01);

      // N
      byte[] buffer = srpKey.getN().toByteArray();
      int length = buffer.length;
      baos.write( length >>> 24        );
      baos.write((length >>> 16) & 0xFF);
      baos.write((length >>>  8) & 0xFF);
      baos.write( length         & 0xFF);
      baos.write(buffer, 0, length);

      // g
      buffer = srpKey.getG().toByteArray();
      length = buffer.length;
      baos.write( length >>> 24        );
      baos.write((length >>> 16) & 0xFF);
      baos.write((length >>>  8) & 0xFF);
      baos.write( length         & 0xFF);
      baos.write(buffer, 0, length);

      // x
      buffer = srpKey.getX().toByteArray();
      length = buffer.length;
      baos.write( length >>> 24        );
      baos.write((length >>> 16) & 0xFF);
      baos.write((length >>>  8) & 0xFF);
      baos.write( length         & 0xFF);
      baos.write(buffer, 0, length);

      // v
      if (srpKey.getV() != null) {
         baos.write(0x01);

         buffer = srpKey.getV().toByteArray();
         length = buffer.length;
         baos.write( length >>> 24        );
         baos.write((length >>> 16) & 0xFF);
         baos.write((length >>>  8) & 0xFF);
         baos.write( length         & 0xFF);
         baos.write(buffer, 0, length);
      } else {
         baos.write(0x00);
      }

      return baos.toByteArray();
   }

   public PrivateKey decodePrivateKey(byte[] k) {
      // magic
      if (k[0] != Registry.MAGIC_RAW_SRP_PRIVATE_KEY[0]
            || k[1] != Registry.MAGIC_RAW_SRP_PRIVATE_KEY[1]
            || k[2] != Registry.MAGIC_RAW_SRP_PRIVATE_KEY[2]
            || k[3] != Registry.MAGIC_RAW_SRP_PRIVATE_KEY[3]) {
         throw new IllegalArgumentException("magic");
      }

      // version
      if (k[4] != 0x01) {
         throw new IllegalArgumentException("version");
      }
      int i = 5;

      int l;
      byte[] buffer;

      // N
      l = k[i++] << 24 | (k[i++] & 0xFF) << 16 | (k[i++] & 0xFF) << 8 | (k[i++] & 0xFF);
      buffer = new byte[l];
      System.arraycopy(k, i, buffer, 0, l);
      i += l;
      BigInteger N = new BigInteger(1, buffer);

      // g
      l = k[i++] << 24 | (k[i++] & 0xFF) << 16 | (k[i++] & 0xFF) << 8 | (k[i++] & 0xFF);
      buffer = new byte[l];
      System.arraycopy(k, i, buffer, 0, l);
      i += l;
      BigInteger g = new BigInteger(1, buffer);

      // x
      l = k[i++] << 24 | (k[i++] & 0xFF) << 16 | (k[i++] & 0xFF) << 8 | (k[i++] & 0xFF);
      buffer = new byte[l];
      System.arraycopy(k, i, buffer, 0, l);
      i += l;
      BigInteger x = new BigInteger(1, buffer);

      // v
      l = k[i++];
      if (l == 0x01) {
         l = k[i++] << 24 | (k[i++] & 0xFF) << 16 | (k[i++] & 0xFF) << 8 | (k[i++] & 0xFF);
         buffer = new byte[l];
         System.arraycopy(k, i, buffer, 0, l);
         i += l;
         BigInteger v = new BigInteger(1, buffer);

         return new SRPPrivateKey(N, g, x, v);
      } else {
         return new SRPPrivateKey(N, g, x);
      }
   }
}
