gcc/libjava/classpath/gnu/java/security/sig/dss/DSSSignatureRawCodec.java

/* DSSSignatureRawCodec.java -- 
   Copyright (C) 2001, 2002, 2003, 2006 Free Software Foundation, Inc.

This file is a part of GNU Classpath.

GNU Classpath 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.

GNU Classpath 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.

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Foundation, Inc., 51 Franklin St, 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
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
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package gnu.java.security.sig.dss;

import gnu.java.security.Registry;
import gnu.java.security.sig.ISignatureCodec;

import java.io.ByteArrayOutputStream;
import java.math.BigInteger;

/**
 * <p>An object that implements the {@link ISignatureCodec} operations for the
 * <i>Raw</i> format to use with DSS signatures.</p>
 */
public class DSSSignatureRawCodec implements ISignatureCodec
{

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

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

  // implicit 0-arguments constructor

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

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

  // gnu.crypto.sig.ISignatureCodec interface implementation -----------------

  public int getFormatID()
  {
    return RAW_FORMAT;
  }

  /**
   * <p>Returns the encoded form of the designated DSS (Digital Signature
   * Standard) signature object according to the <i>Raw</i> format supported by
   * this library.</p>
   *
   * <p>The <i>Raw</i> format for a DSA signature, 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_DSS_SIGNATURE},</li>
   *		<li>1-byte version consisting of the constant: 0x01,</li>
   *		<li>4-byte count of following bytes representing the DSS parameter
   *		<code>r</code> in internet order,</li>
   *		<li>n-bytes representation of a {@link BigInteger} obtained by invoking
   *    the <code>toByteArray()</code> method on the DSS parameter <code>r</code>,</li>
   *		<li>4-byte count of following bytes representing the DSS parameter
   *		<code>s</code>,</li>
   *		<li>n-bytes representation of a {@link BigInteger} obtained by invoking
   *    the <code>toByteArray()</code> method on the DSS parameter <code>s</code>.</li>
   * </ol>
   *
   * @param signature the signature to encode, consisting of the two DSS
   * parameters <code>r</code> and <code>s</code> as a {@link java.math.BigInteger}
   * array.
   * @return the <i>Raw</i> format encoding of the designated signature.
   * @exception IllegalArgumentException if the designated signature is not a
   * DSS (Digital Signature Standard) one.
   */
  public byte[] encodeSignature(Object signature)
  {
    BigInteger r, s;
    try
      {
        BigInteger[] sig = (BigInteger[]) signature;
        r = sig[0];
        s = sig[1];
      }
    catch (Exception x)
      {
        throw new IllegalArgumentException("key");
      }

    ByteArrayOutputStream baos = new ByteArrayOutputStream();

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

    // version
    baos.write(0x01);

    // r
    byte[] buffer = r.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);

    // s
    buffer = s.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 Object decodeSignature(byte[] k)
  {
    // magic
    if (k[0] != Registry.MAGIC_RAW_DSS_SIGNATURE[0]
        || k[1] != Registry.MAGIC_RAW_DSS_SIGNATURE[1]
        || k[2] != Registry.MAGIC_RAW_DSS_SIGNATURE[2]
        || k[3] != Registry.MAGIC_RAW_DSS_SIGNATURE[3])
      {
        throw new IllegalArgumentException("magic");
      }

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

    int i = 5;
    int l;
    byte[] buffer;

    // r
    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 r = new BigInteger(1, buffer);

    // s
    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 s = new BigInteger(1, buffer);

    return new BigInteger[] { r, s };
  }
}