GOST3410KeyPairGenerator.cs :  » PDF » iTextSharp » Org » BouncyCastle » Crypto » Generators » C# / CSharp Open Source

using System;

using Org.BouncyCastle.Asn1.CryptoPro;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Security;

namespace Org.BouncyCastle.Crypto.Generators{
  /**
   * a GOST3410 key pair generator.
   * This generates GOST3410 keys in line with the method described
   * in GOST R 34.10-94.
   */
  public class Gost3410KeyPairGenerator
    : IAsymmetricCipherKeyPairGenerator
  {
    private Gost3410KeyGenerationParameters param;

    public void Init(
      KeyGenerationParameters parameters)
    {
      if (parameters is Gost3410KeyGenerationParameters)
      {
        this.param = (Gost3410KeyGenerationParameters) parameters;
      }
      else
      {
        Gost3410KeyGenerationParameters kgp = new Gost3410KeyGenerationParameters(
          parameters.Random,
          CryptoProObjectIdentifiers.GostR3410x94CryptoProA);

        if (parameters.Strength != kgp.Parameters.P.BitLength - 1)
        {
          // TODO Should we complain?
        }

        this.param = kgp;
      }
    }

    public AsymmetricCipherKeyPair GenerateKeyPair()
    {
      SecureRandom random = param.Random;
      Gost3410Parameters gost3410Params = param.Parameters;

      BigInteger q = gost3410Params.Q;
      BigInteger x;
      do
      {
        x = new BigInteger(256, random);
      }
      while (x.SignValue < 1 || x.CompareTo(q) >= 0);

      BigInteger p = gost3410Params.P;
      BigInteger a = gost3410Params.A;

      // calculate the public key.
      BigInteger y = a.ModPow(x, p);

      if (param.PublicKeyParamSet != null)
      {
        return new AsymmetricCipherKeyPair(
          new Gost3410PublicKeyParameters(y, param.PublicKeyParamSet),
          new Gost3410PrivateKeyParameters(x, param.PublicKeyParamSet));
      }

      return new AsymmetricCipherKeyPair(
        new Gost3410PublicKeyParameters(y, gost3410Params),
        new Gost3410PrivateKeyParameters(x, gost3410Params));
    }
  }
}