using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.IO;

using System.Text;

using Org.BouncyCastle.Crypto;

using Org.BouncyCastle.Crypto.Engines;

using Org.BouncyCastle.Crypto.Generators;

using Org.BouncyCastle.Crypto.Modes;

using Org.BouncyCastle.Crypto.Parameters;

using Org.BouncyCastle.Security;

using Org.BouncyCastle.Crypto.Paddings;

using System.Security.Cryptography;

​

namespace ConsoleApp1

{

    class Program

    {

        static byte[] IV = Encoding.UTF32.GetBytes("XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX");

​

​

        static void Main(string[] args)

        {

            var encoding = new UTF32Encoding();

​

            Encoding _encoding;

            IBlockCipherPadding _padding;

            byte[] key = StringToByteArray("4C84C1898FC592F192C8059215F6AB8068D480CC3B8579438532947703067A731781F75B450412B910076C20CE0670274705031F245EC56B14301F54338ED7BFE52A0692DF014A5E01660D3E30D33DB03D41F836354F5A5AB23BDA5F92585314");

            byte[] ciphertxt = encoding.GetBytes("0000000000000000000000000000000000000000000000000000000000000000");

​

            DecryptAnother(ciphertxt, key);

​

            Console.ReadKey();

        }

​

​

        public static byte[] kdf(byte[] z, byte[] otherInfo)

        {

             // C# BC

            IDigest digest = new Sha256Digest();

            byte[] result = new byte[digest.GetDigestSize()];

            digest.Update((byte)(1 >> 24));

            digest.Update((byte)(1 >> 16));

            digest.Update((byte)(1 >> 8));

            digest.Update((byte)1);

            digest.BlockUpdate(z, 0, z.Length);

            digest.BlockUpdate(otherInfo, 0, otherInfo.Length);

            digest.DoFinal(result, 0);

​

            return result;

        }

​

        public static void DecryptAnother(byte[] ciphertxt, byte[] key)

        {

            byte[] aesKeyData = kdf(key, ciphertxt);

            var cipher = new GcmBlockCipher(new AesFastEngine());

            KeyParameter keyParameter = ParameterUtilities.CreateKeyParameter("AES", aesKeyData);

            ICipherParameters cipherParameters = new ParametersWithIV(keyParameter, IV);

            cipher.Init(false, cipherParameters);

​

            byte[] output = new byte[cipher.GetOutputSize(ciphertxt.Length)];

            int len = cipher.ProcessBytes(ciphertxt, 0, ciphertxt.Length, output, 0);

            try

            {

                Console.WriteLine(cipher.DoFinal(output, len));

            }

            catch (Exception ex)

            {

                Console.WriteLine(ex.Message);

            }

        }

​

​

        private static byte[] StringToByteArray(string HexString)

        {

​

            int NumberChars = HexString.Length;

            byte[] bytes = new byte[NumberChars / 2];

            for (int i = 0; i < NumberChars; i += 2)

            {

                bytes[i / 2] = Convert.ToByte(HexString.Substring(i, 2), 16);

            }

            return bytes;

        }

    }

}

​