ElGamalKeyPairGenerator.cs :  » PDF » iTextSharp » Org » BouncyCastle » Crypto » Generators » C# / CSharp Open Source

using System;

using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Math;

namespace Org.BouncyCastle.Crypto.Generators{
    /**
     * a ElGamal key pair generator.
     * <p>
     * This Generates keys consistent for use with ElGamal as described in
     * page 164 of "Handbook of Applied Cryptography".</p>
     */
    public class ElGamalKeyPairGenerator
    : IAsymmetricCipherKeyPairGenerator
    {
        private ElGamalKeyGenerationParameters param;

        public void Init(
      KeyGenerationParameters parameters)
        {
            this.param = (ElGamalKeyGenerationParameters) parameters;
        }

        public AsymmetricCipherKeyPair GenerateKeyPair()
        {
      DHKeyGeneratorHelper helper = DHKeyGeneratorHelper.Instance;
      ElGamalParameters egp = param.Parameters;
      DHParameters dhp = new DHParameters(egp.P, egp.G, null, 0, egp.L);

      BigInteger x = helper.CalculatePrivate(dhp, param.Random);
      BigInteger y = helper.CalculatePublic(dhp, x);

      return new AsymmetricCipherKeyPair(
                new ElGamalPublicKeyParameters(y, egp),
                new ElGamalPrivateKeyParameters(x, egp));
        }
    }

}