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      1 package org.bouncycastle.jcajce.provider.asymmetric.dsa;
      2 
      3 import java.security.AlgorithmParameters;
      4 import java.security.InvalidAlgorithmParameterException;
      5 import java.security.InvalidParameterException;
      6 import java.security.SecureRandom;
      7 import java.security.spec.AlgorithmParameterSpec;
      8 import java.security.spec.DSAParameterSpec;
      9 
     10 import org.bouncycastle.crypto.digests.SHA256Digest;
     11 import org.bouncycastle.crypto.generators.DSAParametersGenerator;
     12 import org.bouncycastle.crypto.params.DSAParameterGenerationParameters;
     13 import org.bouncycastle.crypto.params.DSAParameters;
     14 import org.bouncycastle.jcajce.provider.asymmetric.util.BaseAlgorithmParameterGeneratorSpi;
     15 import org.bouncycastle.jcajce.provider.asymmetric.util.PrimeCertaintyCalculator;
     16 
     17 public class AlgorithmParameterGeneratorSpi
     18     extends BaseAlgorithmParameterGeneratorSpi
     19 {
     20     protected SecureRandom random;
     21     // Android-changed: Change default strength to 1024
     22     // In 1.57, the default strength was changed to 2048.  We keep it at 1024 for app
     23     // compatibility, particularly because the default digest (SHA-1) doesn't have
     24     // a sufficiently long digest to work with 2048-bit keys.
     25     protected int strength = 1024;
     26     protected DSAParameterGenerationParameters params;
     27 
     28     protected void engineInit(
     29         int strength,
     30         SecureRandom random)
     31     {
     32         if (strength < 512 || strength > 3072)
     33         {
     34             throw new InvalidParameterException("strength must be from 512 - 3072");
     35         }
     36 
     37         if (strength <= 1024 && strength % 64 != 0)
     38         {
     39             throw new InvalidParameterException("strength must be a multiple of 64 below 1024 bits.");
     40         }
     41 
     42         if (strength > 1024 && strength % 1024 != 0)
     43         {
     44             throw new InvalidParameterException("strength must be a multiple of 1024 above 1024 bits.");
     45         }
     46 
     47         this.strength = strength;
     48         this.random = random;
     49     }
     50 
     51     protected void engineInit(
     52         AlgorithmParameterSpec genParamSpec,
     53         SecureRandom random)
     54         throws InvalidAlgorithmParameterException
     55     {
     56         throw new InvalidAlgorithmParameterException("No supported AlgorithmParameterSpec for DSA parameter generation.");
     57     }
     58 
     59     protected AlgorithmParameters engineGenerateParameters()
     60     {
     61         DSAParametersGenerator pGen;
     62 
     63         if (strength <= 1024)
     64         {
     65             pGen = new DSAParametersGenerator();
     66         }
     67         else
     68         {
     69             pGen = new DSAParametersGenerator(new SHA256Digest());
     70         }
     71 
     72         if (random == null)
     73         {
     74             random = new SecureRandom();
     75         }
     76 
     77         int certainty = PrimeCertaintyCalculator.getDefaultCertainty(strength);
     78 
     79         if (strength == 1024)
     80         {
     81             params = new DSAParameterGenerationParameters(1024, 160, certainty, random);
     82             pGen.init(params);
     83         }
     84         else if (strength > 1024)
     85         {
     86             params = new DSAParameterGenerationParameters(strength, 256, certainty, random);
     87             pGen.init(params);
     88         }
     89         else
     90         {
     91             pGen.init(strength, certainty, random);
     92         }
     93 
     94         DSAParameters p = pGen.generateParameters();
     95 
     96         AlgorithmParameters params;
     97 
     98         try
     99         {
    100             params = createParametersInstance("DSA");
    101             params.init(new DSAParameterSpec(p.getP(), p.getQ(), p.getG()));
    102         }
    103         catch (Exception e)
    104         {
    105             throw new RuntimeException(e.getMessage());
    106         }
    107 
    108         return params;
    109     }
    110 }
    111