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.classpath.SystemProperties;
  42 import gnu.java.security.Registry;
  43 import gnu.java.security.key.IKeyPairCodec;
  44
  45 import java.math.BigInteger;
  46 import java.security.PublicKey;
  47 import java.security.interfaces.DSAPublicKey;
  48
  49 /**
  50  * <p>An object that embodies a DSS (Digital Signature Standard) public key.</p>
  51  *
  52  * @see #getEncoded
  53  */
  54 public class DSSPublicKey extends DSSKey implements PublicKey, DSAPublicKey
  55 {
  56   // Constants and variables
  57   // -------------------------------------------------------------------------
  58
  59   /**
  60    * <code>y = g<sup>x</sup> mod p</code> where <code>x</code> is the private
  61    * 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   // Constructor(s)
  69   // -------------------------------------------------------------------------
  70
  71   /**
  72    * Conveience constructor. Calls the constructor with 5 arguments passing
  73    * {@link Registry#RAW_ENCODING_ID} as the identifier of the preferred
  74    * encoding format.
  75    *
  76    * @param p the public modulus.
  77    * @param q the public prime divisor of <code>p-1</code>.
  78    * @param g a generator of the unique cyclic group <code>Z<sup>*</sup>
  79    *          <sub>p</sub></code>.
  80    * @param y the public key part.
  81    */
  82   public DSSPublicKey(BigInteger p, BigInteger q, BigInteger g, BigInteger y)
  83   {
  84     this(Registry.RAW_ENCODING_ID, p, q, g, y);
  85   }
  86
  87   /**
  88    * Constructs a new instance of <code>DSSPublicKey</code> given the designated
  89    * arguments.
  90    *
  91    * @param preferredFormat the identifier of the preferred encoding format to
  92    *          use when externalizing this key.
  93    * @param p the public modulus.
  94    * @param q the public prime divisor of <code>p-1</code>.
  95    * @param g a generator of the unique cyclic group <code>Z<sup>*</sup>
  96    *          <sub>p</sub></code>.
  97    * @param y the public key part.
  98    */
  99   public DSSPublicKey(int preferredFormat, BigInteger p, BigInteger q,
 100                       BigInteger g, BigInteger y)
 101   {
 102     super(preferredFormat == Registry.ASN1_ENCODING_ID ? Registry.X509_ENCODING_ID
 103                                                        : preferredFormat,
 104           p, q, g);
 105
 106     this.y = y;
 107   }
 108
 109   // Class methods
 110   // -------------------------------------------------------------------------
 111
 112   /**
 113    * A class method that takes the output of the <code>encodePublicKey()</code>
 114    * method of a DSS keypair codec object (an instance implementing
 115    * {@link gnu.java.security.key.IKeyPairCodec} for DSS keys, and re-constructs
 116    * an instance of this object.
 117    *
 118    * @param k the contents of a previously encoded instance of this object.
 119    * @exception ArrayIndexOutOfBoundsException if there is not enough bytes, in
 120    *              <code>k</code>, to represent a valid encoding of an
 121    *              instance of this object.
 122    * @exception IllegalArgumentException if the byte sequence does not represent
 123    *              a valid encoding of an instance of this object.
 124    */
 125   public static DSSPublicKey valueOf(byte[] k)
 126   {
 127     // try RAW codec
 128     if (k[0] == Registry.MAGIC_RAW_DSS_PUBLIC_KEY[0])
 129       try
 130         {
 131           return (DSSPublicKey) new DSSKeyPairRawCodec().decodePublicKey(k);
 132         }
 133       catch (IllegalArgumentException ignored)
 134         {
 135         }
 136
 137     // try X.509 codec
 138     return (DSSPublicKey) new DSSKeyPairX509Codec().decodePublicKey(k);
 139   }
 140
 141   // Instance methods
 142   // -------------------------------------------------------------------------
 143
 144   // java.security.interfaces.DSAPublicKey interface implementation ----------
 145
 146   public BigInteger getY()
 147   {
 148     return y;
 149   }
 150
 151   // Other instance methods --------------------------------------------------
 152
 153   /**
 154    * <p>Returns the encoded form of this public key according to the designated
 155    * format.</p>
 156    *
 157    * @param format the desired format identifier of the resulting encoding.
 158    * @return the byte sequence encoding this key according to the designated
 159    * format.
 160    * @exception IllegalArgumentException if the format is not supported.
 161    * @see DSSKeyPairRawCodec
 162    */
 163   public byte[] getEncoded(int format)
 164   {
 165     byte[] result;
 166     switch (format)
 167       {
 168       case IKeyPairCodec.RAW_FORMAT:
 169         result = new DSSKeyPairRawCodec().encodePublicKey(this);
 170         break;
 171       case IKeyPairCodec.X509_FORMAT:
 172         result = new DSSKeyPairX509Codec().encodePublicKey(this);
 173         break;
 174       default:
 175         throw new IllegalArgumentException("Unsupported encoding format: "
 176                                            + format);
 177       }
 178     return result;
 179   }
 180
 181   /**
 182    * <p>Returns <code>true</code> if the designated object is an instance of
 183    * {@link DSAPublicKey} and has the same DSS (Digital Signature Standard)
 184    * parameter values as this one.</p>
 185    *
 186    * @param obj the other non-null DSS key to compare to.
 187    * @return <code>true</code> if the designated object is of the same type and
 188    * value as this one.
 189    */
 190   public boolean equals(Object obj)
 191   {
 192     if (obj == null)
 193       {
 194         return false;
 195       }
 196     if (!(obj instanceof DSAPublicKey))
 197       {
 198         return false;
 199       }
 200     DSAPublicKey that = (DSAPublicKey) obj;
 201     return super.equals(that) && y.equals(that.getY());
 202   }
 203
 204   public String toString()
 205   {
 206     if (str == null)
 207       {
 208         String ls = SystemProperties.getProperty("line.separator");
 209         str = new StringBuilder(this.getClass().getName()).append("(")
 210         .append(super.toString()).append(",").append(ls)
 211         .append("y=0x").append(y.toString(16)).append(ls)
 212         .append(")").toString();
 213       }
 214
 215     return str;
 216   }
 217 }