trunk/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.action.GetPropertyAction;
  43 import gnu.java.security.key.IKeyPairCodec;
  44
  45 import java.math.BigInteger;
  46 import java.security.AccessController;
  47
  48 import javax.crypto.interfaces.DHPublicKey;
  49
  50 /**
  51  * An implementation of the Diffie-Hellman public key.
  52  * <p>
  53  * Reference:
  54  * <ol>
  55  * <li><a href="http://www.ietf.org/rfc/rfc2631.txt">Diffie-Hellman Key
  56  * Agreement Method</a><br>
  57  * Eric Rescorla.</li>
  58  * </ol>
  59  */
  60 public class GnuDHPublicKey
  61     extends GnuDHKey
  62     implements DHPublicKey
  63 {
  64   private BigInteger y;
  65   /** String representation of this key. Cached for speed. */
  66   private transient String str;
  67
  68   /**
  69    * Convenience constructor. Calls the constructor with five arguments passing
  70    * {@link Registry#RAW_ENCODING_ID} as the value of its first argument.
  71    *
  72    * @param q a prime divisor of p-1.
  73    * @param p the public prime.
  74    * @param g the generator of the group.
  75    * @param y the public value y.
  76    */
  77   public GnuDHPublicKey(BigInteger q, BigInteger p, BigInteger g, BigInteger y)
  78   {
  79     this(Registry.RAW_ENCODING_ID, q, p, g, y);
  80   }
  81
  82   /**
  83    * Constructs a new instance of <code>GnuDHPublicKey</code> given the
  84    * designated parameters.
  85    *
  86    * @param preferredFormat the identifier of the encoding format to use by
  87    *          default when externalizing the key.
  88    * @param q a prime divisor of p-1.
  89    * @param p the public prime.
  90    * @param g the generator of the group.
  91    * @param y the public value y.
  92    */
  93   public GnuDHPublicKey(int preferredFormat, BigInteger q, BigInteger p,
  94                         BigInteger g, BigInteger y)
  95   {
  96     super(preferredFormat == Registry.ASN1_ENCODING_ID ? Registry.X509_ENCODING_ID
  97                                                        : preferredFormat,
  98           q, p, g);
  99     this.y = y;
 100   }
 101
 102   /**
 103    * A class method that takes the output of the <code>encodePublicKey()</code>
 104    * method of a DH keypair codec object (an instance implementing
 105    * {@link IKeyPairCodec} for DSS keys, and re-constructs an instance of this
 106    * object.
 107    *
 108    * @param k the contents of a previously encoded instance of this object.
 109    * @exception ArrayIndexOutOfBoundsException if there is not enough bytes, in
 110    *              <code>k</code>, to represent a valid encoding of an
 111    *              instance of this object.
 112    * @exception IllegalArgumentException if the byte sequence does not represent
 113    *              a valid encoding of an instance of this object.
 114    */
 115   public static GnuDHPublicKey valueOf(byte[] k)
 116   {
 117     // try RAW codec
 118     if (k[0] == Registry.MAGIC_RAW_DH_PUBLIC_KEY[0])
 119       try
 120         {
 121           return (GnuDHPublicKey) new DHKeyPairRawCodec().decodePublicKey(k);
 122         }
 123       catch (IllegalArgumentException ignored)
 124         {
 125         }
 126     // try X.509 codec
 127     return (GnuDHPublicKey) new DHKeyPairX509Codec().decodePublicKey(k);
 128   }
 129
 130   public BigInteger getY()
 131   {
 132     return y;
 133   }
 134
 135   /**
 136    * Returns the encoded form of this public key according to the designated
 137    * format.
 138    *
 139    * @param format the desired format identifier of the resulting encoding.
 140    * @return the byte sequence encoding this key according to the designated
 141    *         format.
 142    * @exception IllegalArgumentException if the format is not supported.
 143    */
 144   public byte[] getEncoded(int format)
 145   {
 146     byte[] result;
 147     switch (format)
 148       {
 149       case IKeyPairCodec.RAW_FORMAT:
 150         result = new DHKeyPairRawCodec().encodePublicKey(this);
 151         break;
 152       case IKeyPairCodec.X509_FORMAT:
 153         result = new DHKeyPairX509Codec().encodePublicKey(this);
 154         break;
 155       default:
 156         throw new IllegalArgumentException("Unsupported encoding format: "
 157                                            + format);
 158       }
 159     return result;
 160   }
 161
 162   /**
 163    * Returns <code>true</code> if the designated object is an instance of
 164    * {@link DHPublicKey} and has the same parameter values as this one.
 165    *
 166    * @param obj the other non-null DH key to compare to.
 167    * @return <code>true</code> if the designated object is of the same type
 168    *         and value as this one.
 169    */
 170   public boolean equals(Object obj)
 171   {
 172     if (obj == null)
 173       return false;
 174
 175     if (! (obj instanceof DHPublicKey))
 176       return false;
 177
 178     DHPublicKey that = (DHPublicKey) obj;
 179     return super.equals(that) && y.equals(that.getY());
 180   }
 181
 182   public String toString()
 183   {
 184     if (str == null)
 185       {
 186         String ls = (String) AccessController.doPrivileged
 187             (new GetPropertyAction("line.separator"));
 188         str = new StringBuilder(this.getClass().getName()).append("(")
 189             .append(super.toString()).append(",").append(ls)
 190             .append("y=0x").append(y.toString(16)).append(ls)
 191             .append(")")
 192             .toString();
 193       }
 194     return str;
 195   }
 196 }