using System;

using System.IO;

using System.Security.Cryptography;

using System.Text;

​

namespace EncryptDecrypt

{

    class Program

    {

        private static byte[] _salt = new byte[32];

        private static String _secret = "fgT45sd7";

        static void Main(string[] args)

        {

            _salt = Encoding.ASCII.GetBytes("o6806642kbM7c5");

            string text = "IE29AIBK93115212345678";

            Console.WriteLine($"Starting text: {text}");

            string encryptedText = EncryptStringAES(text, _secret);

            Console.WriteLine($"Encrypted text: {encryptedText}");

            string finalText = DecryptStringAES(encryptedText, _secret);

            Console.WriteLine($"Decrypted text: {finalText}");

        }

        static public string EncodeTo64(string toEncode)

        {

            byte[] toEncodeAsBytes = ASCIIEncoding.ASCII.GetBytes(toEncode);

            string returnValue = Convert.ToBase64String(toEncodeAsBytes);

            return returnValue;

        }

        public static string EncryptStringAES(string plainText, string sharedSecret)

        {

            // Declare the RijndaelManaged object        

            // used to decrypt the data.        

            RijndaelManaged aesAlg = null;

            // Declare the string used to hold        

            // the decrypted text.        

            string encryptedText = null;

            try

            {

                // Convert the plain text to a byte array

                byte[] plainBytes = Encoding.UTF8.GetBytes(plainText);

                // Generate the key from the shared secret and the salt

                Rfc2898DeriveBytes key = new Rfc2898DeriveBytes(sharedSecret, _salt);

                // Create a RijndaelManaged object with the specified key and IV

                aesAlg = new RijndaelManaged();

                aesAlg.Key = key.GetBytes(aesAlg.KeySize / 8);

                aesAlg.IV = key.GetBytes(aesAlg.BlockSize / 8);

                // Create a encryptor to perform the stream transform

                ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

                // Create the streams used for encryption

                using (MemoryStream msEncrypt = new MemoryStream())

                {

                    using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))

                    {

                        // Write the encrypted bytes to the encrypting stream

                        csEncrypt.Write(plainBytes, 0, plainBytes.Length);

                        csEncrypt.FlushFinalBlock();

                        // Convert the encrypted bytes to a base64 string

                        byte[] encryptedBytes = msEncrypt.ToArray();

                        encryptedText = Convert.ToBase64String(encryptedBytes);

                    }

                }

            }

            finally

            {

                // Clear the RijndaelManaged object.            

                if (aesAlg != null)

                    aesAlg.Clear();

            }

            return encryptedText;

        }

        public static string DecryptStringAES(string cipherText, string sharedSecret)

        {

            //#if DEBUG

            //            return string.Empty;

            //#endif

            if (string.IsNullOrEmpty(cipherText))

                throw new ArgumentNullException("cipherText");

            if (string.IsNullOrEmpty(sharedSecret))

                throw new ArgumentNullException("sharedSecret");

            // Declare the RijndaelManaged object        

            // used to decrypt the data.        

            RijndaelManaged aesAlg = null;

            // Declare the string used to hold        

            // the decrypted text.        

            string plaintext = null;

            try

            {

                // generate the key from the shared secret and the salt            

                Rfc2898DeriveBytes key = new Rfc2898DeriveBytes(sharedSecret, _salt);

                // Create a RijndaelManaged object            

                // with the specified key and IV.            

                aesAlg = new RijndaelManaged();

                aesAlg.Key = key.GetBytes(aesAlg.KeySize / 8);

                aesAlg.IV = key.GetBytes(aesAlg.BlockSize / 8);

                // Create a decrytor to perform the stream transform.            

                ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);

                // Create the streams used for decryption.                            

                byte[] bytes = Convert.FromBase64String(cipherText);

                using (MemoryStream msDecrypt = new MemoryStream(bytes))

                {

                    using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))

                    {

                        using (StreamReader srDecrypt = new StreamReader(csDecrypt))

                            // Read the decrypted bytes from the decrypting stream                         

                            // and place them in a string.                        

                            plaintext = srDecrypt.ReadToEnd();

                    }

                }

            }

            finally

            {

                // Clear the RijndaelManaged object.            

                if (aesAlg != null)

                    aesAlg.Clear();

            }

            return plaintext;

        }

    }

}