An Encrypted String Data Type for Visual Studio LightSwitch: Listing 5

C# version of EncryptedString.vb

internal class EncryptionMethods
{
  //using System.IO;
  //using System.Reflection;
  //using System.Security.Cryptography;
  //using System.Text;

  private byte[] Key;
  private byte[] IV;

  internal EncryptionMethods()
  {
    // Pay performance hit to create pseudo-random password and salt
    // only at initialization
    string Password = Assembly.GetExecutingAssembly().GetType().GUID.ToString().Replace("-", "");
      SetKeyAndIV(Password);
  }

  private void SetKeyAndIV(string Password)
  {
    try
    {
      // Set the key and salt based on the Assembly GUID
      string Salt = Password.Substring(Password.Length - 16);

      byte[] bytPassword = UTF8Encoding.UTF8.GetBytes(Password);
      byte[] bytSalt = UTF8Encoding.UTF8.GetBytes(Salt);
      Rfc2898DeriveBytes rfc2898 = new Rfc2898DeriveBytes(bytPassword, bytSalt, 10000);
      Key = rfc2898.GetBytes(32);
      IV = rfc2898.GetBytes(16);
    }
    catch (Exception ex)
    {
      throw new Exception("Set Key and IV String Error", ex);
    }
  }

  internal string DecryptString(string EncryptedText)
  {
    string result = string.Empty;
    byte[] bytEncryptedText = Convert.FromBase64String(EncryptedText);

    try
    {
      using (AesManaged aes = new AesManaged())
      {
        aes.Key = Key;
        aes.IV = IV;

        ICryptoTransform decryptor = aes.CreateDecryptor(aes.Key, aes.IV);
        using (MemoryStream msDecrypt = new MemoryStream(bytEncryptedText))
        {
          using (CryptoStream csDecrypt = 
            new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
          {
            using (StreamReader srDecrypt = new StreamReader(csDecrypt))
            {
              result = srDecrypt.ReadToEnd();
            }
          }
        }
      }
    }
    catch (Exception ex)
    {
      throw new Exception("Decrypt String Error", ex);
    }
    return result;
  }

  internal string EncryptString(string PlainText)
  {
    string result = string.Empty;
    byte[] bytEncrypted;

    try
    {
      using (AesManaged aes = new AesManaged())
      {
        aes.Key = Key;
        aes.IV = IV;

        ICryptoTransform encryptor = aes.CreateEncryptor(aes.Key, aes.IV);
        using (MemoryStream msEncrypt = new MemoryStream())
        {
          using (CryptoStream csEncrypt = 
            new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
          {
            using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
          {
            swEncrypt.Write(PlainText);
          }
          bytEncrypted = msEncrypt.ToArray();
          result = Convert.ToBase64String(bytEncrypted);
        }
      }
    }
  }
  catch (Exception ex)
  {
    throw new Exception("Encrypt String Error", ex);
  }
  return result;
  }
}

About the Author

Joe Kunk is a Microsoft MVP in Visual Basic, three-time president of the Greater Lansing User Group for .NET, and developer for Dart Container Corporation of Mason, Michigan. He's been developing software for over 30 years and has worked in the education, government, financial and manufacturing industries. Kunk's co-authored the book "Professional DevExpress ASP.NET Controls" (Wrox Programmer to Programmer, 2009). He can be reached via email at joekunk@gmail.com.