using System;

using System.IO;

using System.Security.Cryptography;

using System.Text;

​

public class Program

{

    private static byte[] key = new byte[] { 0x12, 0x34, 0x56, 0x78, 0x9A, 0xBC, 0xDE, 0xF0, 0x12, 0x34, 0x56, 0x78, 0x9A, 0xBC, 0xDE, 0xF0, 0x12, 0x34, 0x56, 0x78, 0x9A, 0xBC, 0xDE, 0xF0, 0x12, 0x34, 0x56, 0x78, 0x9A, 0xBC, 0xDE, 0xF0 };

    private static byte[] iv = new byte[] { 0x02, 0x13, 0x24, 0x35, 0x46, 0x57, 0x68, 0x79, 0x8A, 0x9B, 0xAC, 0xBD, 0xCE, 0xDF, 0xE0, 0xF1 };

​

    public static void Main()

    {

        // EncB64 ciphertext: fails

        try

        {

            string ciphertextEncB64 = "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";

            byte[] ciphertextDecB64 = Convert.FromBase64String(ciphertextEncB64);

            Console.WriteLine("Test 1: Plaintext: " + decrypt(ciphertextDecB64));

        }

        catch (Exception ex)

        {

            Console.WriteLine("Test 1: ERROR: " + ex.Message);

        }

        // SBCS, e.g. Cp437: works

        string plaintext = "The quick brown fox jumps over the lazy dog";

        byte[] ciphertext = encrypt(plaintext);

        string ciphertextDecCp437 = Encoding.GetEncoding("cp437").GetString(ciphertext);

        byte[] ciphertextEncCp437 = Encoding.GetEncoding("cp437").GetBytes(ciphertextDecCp437);

        Console.WriteLine("Test 2: Plaintext: " + decrypt(ciphertextEncCp437));

        // MBCS, e.g. UTF-8: fails

        try 

        {   

            string ciphertextDecUtf8 = Encoding.GetEncoding("utf-8").GetString(ciphertext);

            byte[] ciphertextEncUtf8 = Encoding.GetEncoding("utf-8").GetBytes(ciphertextDecUtf8);

            Console.WriteLine("Test 3: Plaintext: " + decrypt(ciphertextEncUtf8));

        }

        catch (Exception ex)

        {

            Console.WriteLine("Test 3: ERROR: " + ex.Message);

        }

   }

​

    private static byte[] encrypt(string body)

    {

        byte[] encrypted;

        using (Aes aesAlg = Aes.Create())

        {

            aesAlg.Key = key;

            aesAlg.IV = iv;

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

            using (MemoryStream msEncrypt = new MemoryStream())

            {

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

                {

                    using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))

                    {

                        swEncrypt.Write(body);

                    }

                    encrypted = msEncrypt.ToArray();

                }

            }

        }

        return encrypted;

    }

​

    private static string decrypt(byte[] encrypted)

    {

        string original = "";

        using (Aes aesAlg = Aes.Create())

        {

            aesAlg.Key = key;

            aesAlg.IV = iv;

            original = DecryptStringFromBytes_Aes(encrypted, aesAlg.Key, aesAlg.IV);

        }

​

        return original;

    }

​

    static string DecryptStringFromBytes_Aes(byte[] cipherText, byte[] Key, byte[] IV)

    {

        if (cipherText == null || cipherText.Length <= 0)

            throw new ArgumentNullException("cipherText");

        if (Key == null || Key.Length <= 0)

            throw new ArgumentNullException("Key");

        if (IV == null || IV.Length <= 0)

            throw new ArgumentNullException("IV");

        string plaintext = null;

        using (Aes aesAlg = Aes.Create())

        {

            aesAlg.Key = Key;

            aesAlg.IV = IV;

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

​

            using (MemoryStream msDecrypt = new MemoryStream(cipherText))

            {

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

                {

                    using (StreamReader srDecrypt = new StreamReader(csDecrypt))

                    {

                        plaintext = srDecrypt.ReadToEnd();

                    }

                }

            }

        }

        return plaintext;

    }

}