Using AES encryption in C#

Answer 1

Look at sample in here..

http://msdn.microsoft.com/en-us/library/system.security.cryptography.rijndaelmanaged(v=VS.100).aspx#Y2262

The example on MSDN does not run normally (an error occurs) because there is no initial value of Initial Vector(iv) and Key. I add 2 line code and now work normally.

More details see below:

using System.Windows.Forms;
using System;
using System.Text;
using System.IO;
using System.Security.Cryptography;

namespace AES_TESTER
{
   public partial class Form1 : Form
   {
       public Form1()
       {
          InitializeComponent();
       }

       private void Form1_Load(object sender, EventArgs e)
       {
          try
          {

            string original = "Here is some data to encrypt!";
            MessageBox.Show("Original:   " + original);

            // Create a new instance of the RijndaelManaged
            // class.  This generates a new key and initialization 
            // vector (IV).
            using (RijndaelManaged myRijndael = new RijndaelManaged())
            {
                 myRijndael.GenerateKey();
                 myRijndael.GenerateIV();

                // Encrypt the string to an array of bytes.
                byte[] encrypted = EncryptStringToBytes(original, myRijndael.Key, myRijndael.IV);

                StringBuilder s = new StringBuilder();
                foreach (byte item in encrypted)
                {
                   s.Append(item.ToString("X2") + " ");
                }
                MessageBox.Show("Encrypted:   " + s);

                // Decrypt the bytes to a string.
                string decrypted = DecryptStringFromBytes(encrypted, myRijndael.Key, myRijndael.IV);

                //Display the original data and the decrypted data.
                MessageBox.Show("Decrypted:    " + decrypted);
            }

        }
        catch (Exception ex)
        {
            MessageBox.Show("Error: {0}", ex.Message);
        }
    }

    static byte[] EncryptStringToBytes(string plainText, byte[] Key, byte[] IV)
    {
        // Check arguments.
        if (plainText == null || plainText.Length <= 0)
            throw new ArgumentNullException("plainText");
        if (Key == null || Key.Length <= 0)
            throw new ArgumentNullException("Key");
        if (IV == null || IV.Length <= 0)
            throw new ArgumentNullException("Key");
        byte[] encrypted;
        // Create an RijndaelManaged object
        // with the specified key and IV.
        using (RijndaelManaged rijAlg = new RijndaelManaged())
        {
            rijAlg.Key = Key;
            rijAlg.IV = IV;
            rijAlg.Mode = CipherMode.CBC;
            rijAlg.Padding = PaddingMode.Zeros;

            // Create a decrytor to perform the stream transform.
            ICryptoTransform encryptor = rijAlg.CreateEncryptor(rijAlg.Key, rijAlg.IV);

            // Create the streams used for encryption.
            using (MemoryStream msEncrypt = new MemoryStream())
            {
                using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                {
                    using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                    {

                        //Write all data to the stream.
                        swEncrypt.Write(plainText);
                    }
                    encrypted = msEncrypt.ToArray();
                }
            }
        }


        // Return the encrypted bytes from the memory stream.
        return encrypted;

    }

    static string DecryptStringFromBytes(byte[] cipherText, byte[] Key, byte[] IV)
    {
        // Check arguments.
        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("Key");

        // Declare the string used to hold
        // the decrypted text.
        string plaintext = null;

        // Create an RijndaelManaged object
        // with the specified key and IV.
        using (RijndaelManaged rijAlg = new RijndaelManaged())
        {
            rijAlg.Key = Key;
            rijAlg.IV = IV;
            rijAlg.Mode = CipherMode.CBC;
            rijAlg.Padding = PaddingMode.Zeros;

            // Create a decrytor to perform the stream transform.
            ICryptoTransform decryptor = rijAlg.CreateDecryptor(rijAlg.Key, rijAlg.IV);

            // Create the streams used for decryption.
            using (MemoryStream msDecrypt = new MemoryStream(cipherText))
            {
                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();
                    }
                }
            }

        }

        return plaintext;
     }
   }
}