Source for gnu.java.security.key.dss.DSSPublicKey

   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: }