libjava/classpath/gnu/java/security/key/dss/DSSPublicKey.java

   1 /* DSSPublicKey.java --
   2    Copyright 2001, 2002, 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.java.security.key.dss;
  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 import java.security.PublicKey;
  48 import java.security.interfaces.DSAPublicKey;
  49
  50 /**
  51  * An object that embodies a DSS (Digital Signature Standard) public key.
  52  *
  53  * @see #getEncoded
  54  */
  55 public class DSSPublicKey
  56     extends DSSKey
  57     implements PublicKey, DSAPublicKey
  58 {
  59   /**
  60    * <code>y = g<sup>x</sup> mod p</code> where <code>x</code> is the
  61    * private part of the DSA key.
  62    */
  63   private final BigInteger y;
  64
  65   /** String representation of this key. Cached for speed. */
  66   private transient String str;
  67
  68   /**
  69    * Conveience constructor. Calls the constructor with 5 arguments passing
  70    * {@link Registry#RAW_ENCODING_ID} as the identifier of the preferred
  71    * encoding format.
  72    *
  73    * @param p the public modulus.
  74    * @param q the public prime divisor of <code>p-1</code>.
  75    * @param g a generator of the unique cyclic group <code>Z<sup>*</sup>
  76    *          <sub>p</sub></code>.
  77    * @param y the public key part.
  78    */
  79   public DSSPublicKey(BigInteger p, BigInteger q, BigInteger g, BigInteger y)
  80   {
  81     this(Registry.RAW_ENCODING_ID, p, q, g, y);
  82   }
  83
  84   /**
  85    * Constructs a new instance of <code>DSSPublicKey</code> given the
  86    * designated arguments.
  87    *
  88    * @param preferredFormat the identifier of the preferred encoding format to
  89    *          use when externalizing this key.
  90    * @param p the public modulus.
  91    * @param q the public prime divisor of <code>p-1</code>.
  92    * @param g a generator of the unique cyclic group <code>Z<sup>*</sup>
  93    *          <sub>p</sub></code>.
  94    * @param y the public key part.
  95    */
  96   public DSSPublicKey(int preferredFormat, BigInteger p, BigInteger q,
  97                       BigInteger g, BigInteger y)
  98   {
  99     super(preferredFormat == Registry.ASN1_ENCODING_ID ? Registry.X509_ENCODING_ID
 100                                                        : preferredFormat,
 101           p, q, g);
 102     this.y = y;
 103   }
 104
 105   /**
 106    * A class method that takes the output of the <code>encodePublicKey()</code>
 107    * method of a DSS keypair codec object (an instance implementing
 108    * {@link gnu.java.security.key.IKeyPairCodec} for DSS keys, and re-constructs
 109    * an instance of this object.
 110    *
 111    * @param k the contents of a previously encoded instance of this object.
 112    * @exception ArrayIndexOutOfBoundsException if there is not enough bytes, in
 113    *              <code>k</code>, to represent a valid encoding of an
 114    *              instance of this object.
 115    * @exception IllegalArgumentException if the byte sequence does not represent
 116    *              a valid encoding of an instance of this object.
 117    */
 118   public static DSSPublicKey valueOf(byte[] k)
 119   {
 120     // try RAW codec
 121     if (k[0] == Registry.MAGIC_RAW_DSS_PUBLIC_KEY[0])
 122       try
 123         {
 124           return (DSSPublicKey) new DSSKeyPairRawCodec().decodePublicKey(k);
 125         }
 126       catch (IllegalArgumentException ignored)
 127         {
 128         }
 129     // try X.509 codec
 130     return (DSSPublicKey) new DSSKeyPairX509Codec().decodePublicKey(k);
 131   }
 132
 133   public BigInteger getY()
 134   {
 135     return y;
 136   }
 137
 138   /**
 139    * Returns the encoded form of this public key according to the designated
 140    * format.
 141    *
 142    * @param format the desired format identifier of the resulting encoding.
 143    * @return the byte sequence encoding this key according to the designated
 144    *         format.
 145    * @exception IllegalArgumentException if the format is not supported.
 146    * @see DSSKeyPairRawCodec
 147    */
 148   public byte[] getEncoded(int format)
 149   {
 150     byte[] result;
 151     switch (format)
 152       {
 153       case IKeyPairCodec.RAW_FORMAT:
 154         result = new DSSKeyPairRawCodec().encodePublicKey(this);
 155         break;
 156       case IKeyPairCodec.X509_FORMAT:
 157         result = new DSSKeyPairX509Codec().encodePublicKey(this);
 158         break;
 159       default:
 160         throw new IllegalArgumentException("Unsupported encoding format: "
 161                                            + format);
 162       }
 163     return result;
 164   }
 165
 166   /**
 167    * Returns <code>true</code> if the designated object is an instance of
 168    * {@link DSAPublicKey} and has the same DSS (Digital Signature Standard)
 169    * parameter values as this one.
 170    *
 171    * @param obj the other non-null DSS key to compare to.
 172    * @return <code>true</code> if the designated object is of the same type
 173    *         and value as this one.
 174    */
 175   public boolean equals(Object obj)
 176   {
 177     if (obj == null)
 178       return false;
 179
 180     if (! (obj instanceof DSAPublicKey))
 181       return false;
 182
 183     DSAPublicKey that = (DSAPublicKey) obj;
 184     return super.equals(that) && y.equals(that.getY());
 185   }
 186
 187   public String toString()
 188   {
 189     if (str == null)
 190       {
 191         String ls = (String) AccessController.doPrivileged
 192             (new GetPropertyAction("line.separator"));
 193         str = new StringBuilder(this.getClass().getName()).append("(")
 194             .append(super.toString()).append(",").append(ls)
 195             .append("y=0x").append(y.toString(16)).append(ls)
 196             .append(")")
 197             .toString();
 198       }
 199     return str;
 200   }
 201 }