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

using System;

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

namespace Org.BouncyCastle.Crypto.Generators{
    public class ElGamalParametersGenerator
    {
    private int        size;
        private int        certainty;
        private SecureRandom  random;

    public void Init(
            int        size,
            int        certainty,
            SecureRandom  random)
        {
            this.size = size;
            this.certainty = certainty;
            this.random = random;
        }

    /**
         * which Generates the p and g values from the given parameters,
         * returning the ElGamalParameters object.
         * <p>
         * Note: can take a while...
     * </p>
         */
        public ElGamalParameters GenerateParameters()
        {
      //
      // find a safe prime p where p = 2*q + 1, where p and q are prime.
      //
      BigInteger[] safePrimes = DHParametersHelper.GenerateSafePrimes(size, certainty, random);

      BigInteger p = safePrimes[0];
      BigInteger q = safePrimes[1];
      BigInteger g = DHParametersHelper.SelectGenerator(p, q, random);

      return new ElGamalParameters(p, g);
        }
    }
}