libjava/classpath/gnu/javax/crypto/key/srp6/SRPKey.java

   1 /* SRPKey.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.srp6;
  40
  41 import gnu.java.security.Registry;
  42 import gnu.java.security.key.IKeyPairCodec;
  43
  44 import java.io.Serializable;
  45 import java.math.BigInteger;
  46 import java.security.Key;
  47
  48 /**
  49  * <p>An abstract representation of a base SRP ephemeral key.</p>
  50  *
  51  * <p>This object encapsulates the two numbers:</p>
  52  * <ul>
  53  *    <li><b>N</b>: A large safe prime (N = 2q+1, where q is prime).</li>
  54  *    <li><b>g</b>: A generator modulo N.</li>
  55  * </ul>
  56  *
  57  * <p>Note that in SRP, all arithmetic is done modulo N.</p>
  58  *
  59  * <p>Reference:</p>
  60  * <ol>
  61  *    <li><a href="http://srp.stanford.edu/design.html">SRP Protocol Design</a><br>
  62  *    Thomas J. Wu.</li>
  63  * </ol>
  64  */
  65 public abstract class SRPKey implements Key, Serializable
  66 {
  67
  68   // Constants and variables
  69   // -------------------------------------------------------------------------
  70
  71   /** The public, Germaine prime, shared modulus. */
  72   protected final BigInteger N;
  73
  74   /** The generator. */
  75   protected final BigInteger g;
  76
  77   // Constructor(s)
  78   // -------------------------------------------------------------------------
  79
  80   protected SRPKey(BigInteger N, BigInteger g)
  81   {
  82     super();
  83
  84     this.N = N;
  85     this.g = g;
  86   }
  87
  88   // Class methods
  89   // -------------------------------------------------------------------------
  90
  91   // Instance methods
  92   // -------------------------------------------------------------------------
  93
  94   // java.security.Key interface implementation ------------------------------
  95
  96   /**
  97    * <p>Returns the standard algorithm name for this key.</p>
  98    *
  99    * @return the standard algorithm name for this key.
 100    */
 101   public String getAlgorithm()
 102   {
 103     return Registry.SRP_KPG;
 104   }
 105
 106   /** @deprecated see getEncoded(int). */
 107   public byte[] getEncoded()
 108   {
 109     return getEncoded(IKeyPairCodec.RAW_FORMAT);
 110   }
 111
 112   /**
 113    * Returns {@link Registry#RAW_ENCODING_SHORT_NAME} which is the sole format
 114    * supported for this type of keys.
 115    *
 116    * @return {@link Registry#RAW_ENCODING_SHORT_NAME} ALWAYS.
 117    */
 118   public String getFormat()
 119   {
 120     return Registry.RAW_ENCODING_SHORT_NAME;
 121   }
 122
 123   // other methods -----------------------------------------------------------
 124
 125   /**
 126    * <p>Returns the public shared modulus.</p>
 127    *
 128    * @return <code>N</code>.
 129    */
 130   public BigInteger getN()
 131   {
 132     return N;
 133   }
 134
 135   /**
 136    * <p>Returns the generator.</p>
 137    *
 138    * @return <code>g</code>.
 139    */
 140   public BigInteger getG()
 141   {
 142     return g;
 143   }
 144
 145   /**
 146    * <p>Returns <code>true</code> if the designated object is an instance of
 147    * <code>SRPKey</code> and has the same SRP parameter values as this one.</p>
 148    *
 149    * @param obj the other non-null SRP key to compare to.
 150    * @return <code>true</code> if the designated object is of the same type and
 151    * value as this one.
 152    */
 153   public boolean equals(Object obj)
 154   {
 155     if (obj == null)
 156       {
 157         return false;
 158       }
 159     if (!(obj instanceof SRPKey))
 160       {
 161         return false;
 162       }
 163     SRPKey that = (SRPKey) obj;
 164     return N.equals(that.getN()) && g.equals(that.getG());
 165   }
 166
 167   // abstract methods to be implemented by subclasses ------------------------
 168
 169   public abstract byte[] getEncoded(int format);
 170 }