libjava/classpath/gnu/java/security/provider/DSAParameterGenerator.java

   1 /* DSAParameterGenerator.java --- DSA Parameter Generator Implementation
   2    Copyright (C) 1999 Free Software Foundation, Inc.
   3
   4 This file is 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, or (at your option)
   9 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; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 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.provider;
  40
  41 import gnu.java.security.util.Prime;
  42
  43 import java.math.BigInteger;
  44 import java.security.AlgorithmParameterGeneratorSpi;
  45 import java.security.AlgorithmParameters;
  46 import java.security.InvalidAlgorithmParameterException;
  47 import java.security.NoSuchAlgorithmException;
  48 import java.security.SecureRandom;
  49 import java.security.spec.AlgorithmParameterSpec;
  50 import java.security.spec.DSAParameterSpec;
  51 import java.security.spec.InvalidParameterSpecException;
  52 import java.util.Random;
  53
  54 public class DSAParameterGenerator extends AlgorithmParameterGeneratorSpi
  55 {
  56   private int size;
  57   private SecureRandom random = null;
  58
  59   public DSAParameterGenerator()
  60   {
  61     size = 1024;
  62   }
  63
  64   public void engineInit(int size, SecureRandom random)
  65   {
  66     if( (size < 512) || (size > 1024) || ( (size % 64) != 0) )
  67       //throw new InvalidAlgorithmParameterException("Invalid Size");
  68       return;
  69     this.size = size;
  70     this.random = random;
  71   }
  72
  73   public void engineInit(AlgorithmParameterSpec genParamSpec, SecureRandom random)
  74     throws InvalidAlgorithmParameterException
  75   {
  76     if( !( genParamSpec instanceof DSAParameterSpec ) )
  77       throw new InvalidAlgorithmParameterException("Must be DSAParameterSpec");
  78
  79     DSAParameterSpec dsaparameterspec = (DSAParameterSpec)genParamSpec;
  80     int tmp = dsaparameterspec.getP().bitLength();
  81
  82     if( (tmp < 512) || (tmp > 1024) || ( (tmp % 64) != 0) )
  83       throw new InvalidAlgorithmParameterException("Invalid Size");
  84
  85     this.random = random;
  86   }
  87
  88   //For more information see IEEE P1363 A.16.1 (10/05/98 Draft)
  89   public AlgorithmParameters engineGenerateParameters()
  90   {
  91     DSAParameterSpec dsaparameterspec;
  92
  93     int L = size;
  94     BigInteger r, p, k, h, g;
  95
  96     //q 2^159 < q < 2^160
  97     r = Prime.generateRandomPrime( 159, 160, BigInteger.valueOf(1));
  98
  99     // 2^(L-1) < p < 2^L
 100     p = Prime.generateRandomPrime( r, BigInteger.valueOf(1), L - 1, L, BigInteger.valueOf(1));
 101
 102     k = p.subtract( BigInteger.valueOf(1) );
 103     k = k.divide( r );
 104
 105     Random rand = new Random();
 106     h = BigInteger.valueOf(1);
 107
 108     for(;;) {
 109       h = h.add(BigInteger.valueOf( 1 ) );
 110
 111       g = h.modPow(k, p);
 112
 113       if( g.compareTo( BigInteger.valueOf(1) ) != 1 )
 114         break;
 115     }
 116
 117     try {
 118       dsaparameterspec = new DSAParameterSpec(p, r, g);
 119       AlgorithmParameters ap = AlgorithmParameters.getInstance("DSA");
 120       ap.init( dsaparameterspec );
 121       return ap;
 122     } catch ( NoSuchAlgorithmException nsae ) {
 123       return null;
 124     } catch ( InvalidParameterSpecException ipse) {
 125       return null;
 126     }
 127   }
 128 }