using System;

using System.IO;

using System.Linq;

using System.Security.Cryptography;

using System.Text;

public class Program

{

    // This constant is used to determine the keysize of the encryption algorithm in bits.

    // We divide this by 8 within the code below to get the equivalent number of bytes.

    private const int Keysize = 256;

​

    // This constant determines the number of iterations for the password bytes generation function.

    private const int DerivationIterations = 1000;

​

    private const string PassPhrase = "3ncrypted#!ims!$p@ss";

​

    public static void Main()

    {

            // encoded password to decrypt

            //string cipherText = "FB0dNmYMqMHPQFeqrFg8gxBv1LkNYBf3B04pLEHVBzE2/23tpVZ8SRHbZsWuQvNAiDz/DLPHr4tzYHnvOh28en2gD3OM6lISTolUiTUlWjSdlezIQkV/usfWLwMPO5gD";

            string cipherText = "1GwTYITIW9lZp08/gDXqw4JSD2Zx1PfC2uxYu+zm8lnWzZreH6FUmyiieh2AhqTeQ65cRO8/a/oYMjwNvtB88at0voPNHebpBlWN99sPTFodFjEd5KpWKFrhrj7xBH+e";

​

            // Get the complete stream of bytes that represent:

            // [32 bytes of Salt] + [32 bytes of IV] + [n bytes of CipherText]

            var cipherTextBytesWithSaltAndIv = Convert.FromBase64String(cipherText);

            // Get the saltbytes by extracting the first 32 bytes from the supplied cipherText bytes.

            var saltStringBytes = cipherTextBytesWithSaltAndIv.Take(Keysize / 8).ToArray();

            // Get the IV bytes by extracting the next 32 bytes from the supplied cipherText bytes.

            var ivStringBytes = cipherTextBytesWithSaltAndIv.Skip(Keysize / 8).Take(Keysize / 8).ToArray();

            // Get the actual cipher text bytes by removing the first 64 bytes from the cipherText string.

            var cipherTextBytes = cipherTextBytesWithSaltAndIv.Skip((Keysize / 8) * 2).Take(cipherTextBytesWithSaltAndIv.Length - ((Keysize / 8) * 2)).ToArray();

​

            using (var password = new Rfc2898DeriveBytes(PassPhrase, saltStringBytes, DerivationIterations))

            {

                var keyBytes = password.GetBytes(Keysize / 8);

                using (var symmetricKey = new RijndaelManaged())

                {

                    symmetricKey.BlockSize = 256;

                    symmetricKey.Mode = CipherMode.CBC;

                    symmetricKey.Padding = PaddingMode.PKCS7;

                    using (var decryptor = symmetricKey.CreateDecryptor(keyBytes, ivStringBytes))

                    {

                        using (var memoryStream = new MemoryStream(cipherTextBytes))

                        {

                            using (var cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))

                            {

                                var plainTextBytes = new byte[cipherTextBytes.Length];

                                var decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);

                                memoryStream.Close();

                                cryptoStream.Close();

                                Console.Write(Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount));

                            }

                        }

                    }

                }

            }

    }

}