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/* DHParameters.java -- DH parameters DAO

   Copyright (C) 2006 Free Software Foundation, Inc.

This file is 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, 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.

You should have received a copy of the GNU General Public License

along with GNU Classpath; 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. */

package gnu.javax.crypto.jce.sig;

import gnu.java.lang.CPStringBuilder;

import gnu.java.security.Registry;

import gnu.java.security.der.DER;

import gnu.java.security.der.DERReader;

import gnu.java.security.der.DERValue;

import gnu.java.security.der.DERWriter;

import gnu.java.security.util.DerUtil;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.math.BigInteger;

import java.security.AlgorithmParametersSpi;

import java.security.spec.AlgorithmParameterSpec;

import java.security.spec.InvalidParameterSpecException;

import java.util.ArrayList;

import javax.crypto.spec.DHGenParameterSpec;

import javax.crypto.spec.DHParameterSpec;

/**

 * A JCE-specific Data Access Object (DAO) for DH parameters.

 */

public class DHParameters

    extends AlgorithmParametersSpi

{

  /** The prime public modulus. */

  private BigInteger p;

  /** The generator. */

  private BigInteger g;

  /** A prime factor of p-1. */

  private BigInteger q;

  /** The (private) random exponent's size (in bits). */

  private int l;

  // default 0-arguments constructor

  protected void engineInit(AlgorithmParameterSpec spec)

      throws InvalidParameterSpecException

  {

    if (! (spec instanceof DHParameterSpec))

      throw new InvalidParameterSpecException("Wrong AlgorithmParameterSpec type: "

                                              + spec.getClass().getName());

    DHParameterSpec dhSpec = (DHParameterSpec) spec;

    p = dhSpec.getP();

    g = dhSpec.getG();

    l = dhSpec.getL();

  }

  /**

   * Decodes the set of DH parameters as per RFC-2459; i.e. the DER-encoded

   * form of the following ASN.1 construct:

   *

   * <pre>

   *   DhParams ::= SEQUENCE {

   *     p  INTEGER, -- odd prime, p=jq +1

   *     g  INTEGER, -- generator, g

   *     q  INTEGER  -- factor of p-1

   *   }

   * </pre>

   */

  protected void engineInit(byte[] params) throws IOException

  {

    DERReader der = new DERReader(params);

    DERValue derParams = der.read();

    DerUtil.checkIsConstructed(derParams, "Wrong DH Parameters field");

    DERValue val = der.read();

    DerUtil.checkIsBigInteger(val, "Wrong P field");

    p = (BigInteger) val.getValue();

    val = der.read();

    DerUtil.checkIsBigInteger(val, "Wrong G field");

    g = (BigInteger) val.getValue();

    val = der.read();

    DerUtil.checkIsBigInteger(val, "Wrong Q field");

    q = (BigInteger) val.getValue();

    l = q.bitLength();

  }

  protected void engineInit(byte[] params, String format) throws IOException

  {

    if (format != null)

      {

        format = format.trim();

        if (format.length() == 0)

          throw new IOException("Format MUST NOT be an empty string");

        if (! format.equalsIgnoreCase(Registry.ASN1_ENCODING_SHORT_NAME))

          throw new IOException("Unknown or unsupported format: " + format);

      }

    engineInit(params);

  }

  protected AlgorithmParameterSpec engineGetParameterSpec(Class paramSpec)

      throws InvalidParameterSpecException

  {

    if (paramSpec.isAssignableFrom(DHParameterSpec.class))

      return new DHParameterSpec(p, g, l);

    if (paramSpec.isAssignableFrom(DHGenParameterSpec.class))

      return new DHGenParameterSpec(p.bitLength(), l);

    throw new InvalidParameterSpecException("Wrong AlgorithmParameterSpec type: "

                                            + paramSpec.getName());

  }

  /**

   * Encodes the set of DH parameters as per RFC-2459; i.e. as the DER-encoded

   * form of the following ASN.1 construct:

   *

   * <pre>

   *   DhParams ::= SEQUENCE {

   *     p  INTEGER, -- odd prime, p=jq +1

   *     g  INTEGER, -- generator, g

   *     q  INTEGER  -- factor of p-1

   *   }

   * </pre>

   */

  protected byte[] engineGetEncoded() throws IOException

  {

    DERValue derP = new DERValue(DER.INTEGER, p);

    DERValue derG = new DERValue(DER.INTEGER, g);

    DERValue derQ = new DERValue(DER.INTEGER, q);

    ArrayList params = new ArrayList(3);

    params.add(derP);

    params.add(derG);

    params.add(derQ);

    DERValue derParams = new DERValue(DER.CONSTRUCTED | DER.SEQUENCE, params);

    ByteArrayOutputStream baos = new ByteArrayOutputStream();

    DERWriter.write(baos, derParams);

    byte[] result = baos.toByteArray();

    return result;

  }

  protected byte[] engineGetEncoded(String format) throws IOException

  {

    if (format != null)

      {

        format = format.trim();

        if (format.length() == 0)

          throw new IOException("Format MUST NOT be an empty string");

        if (! format.equalsIgnoreCase(Registry.ASN1_ENCODING_SHORT_NAME))

          throw new IOException("Unknown or unsupported format: " + format);

      }

    return engineGetEncoded();

  }

  protected String engineToString()

  {

    CPStringBuilder sb = new CPStringBuilder("p=");

    if (p == null)

      sb.append("???");

    else

      sb.append("0x").append(p.toString(16));

    sb.append(", g=");

    if (g == null)

      sb.append("???");

    else

      sb.append("0x").append(g.toString(16));

    sb.append(", q=");

    if (q == null)

      sb.append("???");

    else

      sb.append("0x").append(q.toString(16));

    sb.append(", l=").append(l);

    return sb.toString();

  }

}