libjava/classpath/gnu/javax/crypto/key/dh/GnuDHPublicKey.java

   1 /* GnuDHPublicKey.java --
   2    Copyright (C) 2003, 2006 Free Software Foundation, Inc.
   3
   4 This file is a part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2 of the License, or (at
   9 your option) any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; if not, write to the Free Software
  18 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
  19 USA
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version.  */
  37
  38
  39 package gnu.javax.crypto.key.dh;
  40
  41 import gnu.java.security.Registry;
  42 import gnu.java.security.key.IKeyPairCodec;
  43
  44 import java.math.BigInteger;
  45
  46 import javax.crypto.interfaces.DHPublicKey;
  47
  48 /**
  49  * <p>An implementation of the Diffie-Hellman public key.</p>
  50  *
  51  * <p>Reference:</p>
  52  * <ol>
  53  *    <li><a href="http://www.ietf.org/rfc/rfc2631.txt">Diffie-Hellman Key
  54  *    Agreement Method</a><br>
  55  *    Eric Rescorla.</li>
  56  * </ol>
  57  */
  58 public class GnuDHPublicKey extends GnuDHKey implements DHPublicKey
  59 {
  60
  61   // Constants and variables
  62   // -------------------------------------------------------------------------
  63
  64   private BigInteger y;
  65
  66   // Constructor(s)
  67   // -------------------------------------------------------------------------
  68
  69   /**
  70    * Convenience constructor. Calls the constructor with five arguments passing
  71    * {@link Registry#RAW_ENCODING_ID} as the value of its first argument.
  72    *
  73    * @param q a prime divisor of p-1.
  74    * @param p the public prime.
  75    * @param g the generator of the group.
  76    * @param y the public value y.
  77    */
  78   public GnuDHPublicKey(BigInteger q, BigInteger p, BigInteger g, BigInteger y)
  79   {
  80     this(Registry.RAW_ENCODING_ID, q, p, g, y);
  81   }
  82
  83   /**
  84    * Constructs a new instance of <code>GnuDHPublicKey</code> given the
  85    * designated parameters.
  86    *
  87    * @param preferredFormat the identifier of the encoding format to use by
  88    *          default when externalizing the key.
  89    * @param q a prime divisor of p-1.
  90    * @param p the public prime.
  91    * @param g the generator of the group.
  92    * @param y the public value y.
  93    */
  94   public GnuDHPublicKey(int preferredFormat,
  95                         BigInteger q, BigInteger p, BigInteger g, BigInteger y)
  96   {
  97     super(preferredFormat == Registry.ASN1_ENCODING_ID ? Registry.X509_ENCODING_ID
  98                                                        : preferredFormat,
  99           q, p, g);
 100
 101     this.y = y;
 102   }
 103
 104   // Class methods
 105   // -------------------------------------------------------------------------
 106
 107   /**
 108    * <p>A class method that takes the output of the <code>encodePublicKey()</code>
 109    * method of a DH keypair codec object (an instance implementing
 110    * {@link IKeyPairCodec} for DSS keys, and re-constructs an instance of this
 111    * object.</p>
 112    *
 113    * @param k the contents of a previously encoded instance of this object.
 114    * @exception ArrayIndexOutOfBoundsException if there is not enough bytes,
 115    * in <code>k</code>, to represent a valid encoding of an instance of this
 116    * object.
 117    * @exception IllegalArgumentException if the byte sequence does not
 118    * represent a valid encoding of an instance of this object.
 119    */
 120   public static GnuDHPublicKey valueOf(byte[] k)
 121   {
 122     // try RAW codec
 123     if (k[0] == Registry.MAGIC_RAW_DH_PUBLIC_KEY[0])
 124       try
 125         {
 126           return (GnuDHPublicKey) new DHKeyPairRawCodec().decodePublicKey(k);
 127         }
 128       catch (IllegalArgumentException ignored)
 129         {
 130         }
 131
 132     // try X.509 codec
 133     return (GnuDHPublicKey) new DHKeyPairX509Codec().decodePublicKey(k);
 134   }
 135
 136   // Instance methods
 137   // -------------------------------------------------------------------------
 138
 139   // javax.crypto.interfaces.DHPublicKey interface implementation ------------
 140
 141   public BigInteger getY()
 142   {
 143     return y;
 144   }
 145
 146   // other methods -----------------------------------------------------------
 147
 148   /**
 149    * <p>Returns the encoded form of this public key according to the designated
 150    * format.</p>
 151    *
 152    * @param format the desired format identifier of the resulting encoding.
 153    * @return the byte sequence encoding this key according to the designated
 154    * format.
 155    * @exception IllegalArgumentException if the format is not supported.
 156    */
 157   public byte[] getEncoded(int format)
 158   {
 159     byte[] result;
 160     switch (format)
 161       {
 162       case IKeyPairCodec.RAW_FORMAT:
 163         result = new DHKeyPairRawCodec().encodePublicKey(this);
 164         break;
 165       case IKeyPairCodec.X509_FORMAT:
 166         result = new DHKeyPairX509Codec().encodePublicKey(this);
 167         break;
 168       default:
 169         throw new IllegalArgumentException("Unsupported encoding format: "
 170                                            + format);
 171       }
 172     return result;
 173   }
 174
 175   /**
 176    * Returns <code>true</code> if the designated object is an instance of
 177    * {@link DHPublicKey} and has the same parameter values as this one.
 178    *
 179    * @param obj the other non-null DH key to compare to.
 180    * @return <code>true</code> if the designated object is of the same type
 181    *         and value as this one.
 182    */
 183   public boolean equals(Object obj)
 184   {
 185     if (obj == null)
 186       return false;
 187
 188     if (! (obj instanceof DHPublicKey))
 189       return false;
 190
 191     DHPublicKey that = (DHPublicKey) obj;
 192     return super.equals(that) && y.equals(that.getY());
 193   }
 194 }