import org.bouncycastle.crypto.generators.ElGamalParametersGenerator; //导入依赖的package包/类
@Override
public AsymmetricCipherKeyPairGenerator createAsymmetricCipherKeyPairGenerator(final boolean initWithDefaults) {
	final ElGamalKeyPairGenerator generator = new ElGamalKeyPairGenerator();

	if (initWithDefaults) {
		/*
		 * How certain do we want to be that the chosen primes are really primes.
		 * <p>
		 * The higher this number, the more tests are done to make sure they are primes (and not composites).
		 * <p>
		 * See: <a href="http://crypto.stackexchange.com/questions/3114/what-is-the-correct-value-for-certainty-in-rsa-key-pair-generation">What is the correct value for “certainty” in RSA key pair generation?</a>
		 * and
		 * <a href="http://crypto.stackexchange.com/questions/3126/does-a-high-exponent-compensate-for-a-low-degree-of-certainty?lq=1">Does a high exponent compensate for a low degree of certainty?</a>
		 */
		final int certainty = 12;

		final SecureRandom random = new SecureRandom();

		ElGamalParametersGenerator pGen = new ElGamalParametersGenerator();
		pGen.init(4096, certainty, random);
		ElGamalParameters elGamalParameters = pGen.generateParameters();
		generator.init(new ElGamalKeyGenerationParameters(random, elGamalParameters));
	}
	return generator;
}
 

import org.bouncycastle.crypto.generators.ElGamalParametersGenerator; //导入依赖的package包/类
private ElGamalKeyGenerationParameters createElGamalKeyGenerationParameters(final CreatePgpKeyParam createPgpKeyParam) {
	/*
	 * How certain do we want to be that the chosen primes are really primes.
	 * <p>
	 * The higher this number, the more tests are done to make sure they are primes (and not composites).
	 * <p>
	 * See: <a href="http://crypto.stackexchange.com/questions/3114/what-is-the-correct-value-for-certainty-in-rsa-key-pair-generation">What is the correct value for “certainty” in RSA key pair generation?</a>
	 * and
	 * <a href="http://crypto.stackexchange.com/questions/3126/does-a-high-exponent-compensate-for-a-low-degree-of-certainty?lq=1">Does a high exponent compensate for a low degree of certainty?</a>
	 */
	final int certainty = 8; // 12 takes ages - and DSA+El-Gamal is anyway a bad idea and discouraged. Reducing this to make it bearable.

	final SecureRandom random = getSecureRandom();

	ElGamalParametersGenerator pGen = new ElGamalParametersGenerator();
	pGen.init(createPgpKeyParam.getStrength(), certainty, random);
	ElGamalParameters elGamalParameters = pGen.generateParameters();

	// Maybe we should generate our "DH safe primes" only once and store them somewhere? Or maybe we should provide a long list
	// of them in the resources? DHParametersHelper.generateSafePrimes(size, certainty, random); takes really really very long.
	// BUT BEWARE: Attacks on El Gamal can re-use expensively calculated stuff, if p (one of the "safe primes) is the same.
	// However, it is still not *so* easy. Hmmm... don't know. Security is really important here.

	return new ElGamalKeyGenerationParameters(random, elGamalParameters);
}
 

import org.bouncycastle.crypto.generators.ElGamalParametersGenerator; //导入依赖的package包/类
protected AlgorithmParameters engineGenerateParameters()
{
    ElGamalParametersGenerator pGen = new ElGamalParametersGenerator();

    if (random != null)
    {
        pGen.init(strength, 20, random);
    }
    else
    {
        pGen.init(strength, 20, new SecureRandom());
    }

    ElGamalParameters p = pGen.generateParameters();

    AlgorithmParameters params;

    try
    {
        params = AlgorithmParameters.getInstance("ElGamal", BouncyCastleProvider.PROVIDER_NAME);
        params.init(new DHParameterSpec(p.getP(), p.getG(), l));
    }
    catch (Exception e)
    {
        throw new RuntimeException(e.getMessage());
    }

    return params;
}
 

import org.bouncycastle.crypto.generators.ElGamalParametersGenerator; //导入依赖的package包/类
protected AlgorithmParameters engineGenerateParameters()
     {
         ElGamalParametersGenerator pGen = new ElGamalParametersGenerator();

if ( random != null )
{
	pGen.init(strength, 20, random);
}
else
{
	pGen.init(strength, 20, new SecureRandom());
}

         ElGamalParameters p = pGen.generateParameters();

         AlgorithmParameters params;

         try
         {
             params = AlgorithmParameters.getInstance("ElGamal", BouncyCastleProvider.PROVIDER_NAME);
             params.init(new ElGamalParameterSpec(p.getP(), p.getG()));
         }
         catch (Exception e)
         {
             throw new RuntimeException(e.getMessage());
         }

         return params;
     }
 

import org.bouncycastle.crypto.generators.ElGamalParametersGenerator; //导入依赖的package包/类
protected AlgorithmParameters engineGenerateParameters()
{
    ElGamalParametersGenerator pGen = new ElGamalParametersGenerator();

    if (random != null)
    {
        pGen.init(strength, 20, random);
    }
    else
    {
        pGen.init(strength, 20, new SecureRandom());
    }

    ElGamalParameters p = pGen.generateParameters();

    AlgorithmParameters params;

    try
    {
        params = createParametersInstance("ElGamal");
        params.init(new DHParameterSpec(p.getP(), p.getG(), l));
    }
    catch (Exception e)
    {
        throw new RuntimeException(e.getMessage());
    }

    return params;
}
 

import org.bouncycastle.crypto.generators.ElGamalParametersGenerator; //导入依赖的package包/类
/**
 * this test is can take quiet a while
 *
 * @param size size of key in bits.
 */
private void testGeneration(
    int         size)
{
    ElGamalParametersGenerator       pGen = new ElGamalParametersGenerator();

    pGen.init(size, 10, new SecureRandom());

    ElGamalParameters                elParams = pGen.generateParameters();

    if (elParams.getL() != 0)
    {
        fail("ElGamalParametersGenerator failed to set L to 0 in generated ElGamalParameters");
    }

    ElGamalKeyGenerationParameters   params = new ElGamalKeyGenerationParameters(new SecureRandom(), elParams);

    ElGamalKeyPairGenerator          kpGen = new ElGamalKeyPairGenerator();

    kpGen.init(params);

    //
    // generate first pair
    //
    AsymmetricCipherKeyPair         pair = kpGen.generateKeyPair();

    ElGamalPublicKeyParameters      pu = (ElGamalPublicKeyParameters)pair.getPublic();
    ElGamalPrivateKeyParameters     pv = (ElGamalPrivateKeyParameters)pair.getPrivate();

    ElGamalEngine    e = new ElGamalEngine();

    e.init(true, new ParametersWithRandom(pu, new SecureRandom()));

    byte[]  message = Hex.decode("5468697320697320612074657374");

    byte[]  pText = message;
    byte[]  cText = e.processBlock(pText, 0, pText.length);

    e.init(false, pv);

    pText = e.processBlock(cText, 0, cText.length);

    if (!Arrays.areEqual(message, pText))
    {
        fail("generation test failed");
    }
}