Source for gnu.java.security.provider.DSAParameterGenerator

   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: }