DPAPI - Неизвестный параметр при расшифровке

Есть класс DPAPI

public class DPAPI
{
    [DllImport("crypt32.dll", SetLastError = true, CharSet = System.Runtime.InteropServices.CharSet.Auto)]
    private static extern
        bool CryptProtectData(ref DATA_BLOB pPlainText, string szDescription, ref DATA_BLOB pEntropy, IntPtr pReserved, 
                                         ref CRYPTPROTECT_PROMPTSTRUCT pPrompt, int dwFlags, ref DATA_BLOB pCipherText);
    [DllImport("crypt32.dll", SetLastError = true, CharSet = System.Runtime.InteropServices.CharSet.Auto)]
    private static extern
        bool CryptUnprotectData(ref DATA_BLOB pCipherText, ref string pszDescription, ref DATA_BLOB pEntropy,
              IntPtr pReserved, ref CRYPTPROTECT_PROMPTSTRUCT pPrompt, int dwFlags, ref DATA_BLOB pPlainText);
    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    internal struct DATA_BLOB
    {
        public int cbData;
        public IntPtr pbData;
    }
    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    internal struct CRYPTPROTECT_PROMPTSTRUCT
    {
        public int cbSize;
        public int dwPromptFlags;
        public IntPtr hwndApp;
        public string szPrompt;
    }
    static private IntPtr NullPtr = ((IntPtr)((int)(0)));
    private const int CRYPTPROTECT_UI_FORBIDDEN = 0x1;
    private const int CRYPTPROTECT_LOCAL_MACHINE = 0x4;
    private static void InitPrompt(ref CRYPTPROTECT_PROMPTSTRUCT ps)
    {
        ps.cbSize = Marshal.SizeOf(
                                  typeof(CRYPTPROTECT_PROMPTSTRUCT));
        ps.dwPromptFlags = 0;
        ps.hwndApp = NullPtr;
        ps.szPrompt = null;
    }
    private static void InitBLOB(byte[] data, ref DATA_BLOB blob)
    {
        // Use empty array for null parameter.
        if (data == null)
            data = new byte[0];
        // Allocate memory for the BLOB data.
        blob.pbData = Marshal.AllocHGlobal(data.Length);
        // Make sure that memory allocation was successful.
        if (blob.pbData == IntPtr.Zero)
            throw new Exception(
                "Unable to allocate data buffer for BLOB structure.");
        // Specify number of bytes in the BLOB.
        blob.cbData = data.Length;
        // Copy data from original source to the BLOB structure.
        Marshal.Copy(data, 0, blob.pbData, data.Length);
    }
    public enum KeyType { UserKey = 1, MachineKey };
    private static KeyType defaultKeyType = KeyType.UserKey;
    public static string Encrypt(string plainText)
    {
        return Encrypt(defaultKeyType, plainText, String.Empty, String.Empty);
    }
    public static string Encrypt(KeyType keyType, string plainText)
    {
        return Encrypt(keyType, plainText, String.Empty,
                        String.Empty);
    }
    public static string Encrypt(KeyType keyType, string plainText, string entropy)
    {
        return Encrypt(keyType, plainText, entropy, String.Empty);
    }
    public static string Encrypt(KeyType keyType, string plainText, string entropy, string description)
    {
        // Make sure that parameters are valid.
        if (plainText == null) plainText = String.Empty;
        if (entropy == null) entropy = String.Empty;
        // Call encryption routine and convert returned bytes into
        // a base64-encoded value.
        return Convert.ToBase64String(
                Encrypt(keyType,
                        Encoding.UTF8.GetBytes(plainText),
                        Encoding.UTF8.GetBytes(entropy),
                        description));
    }
    public static byte[] Encrypt(KeyType keyType, byte[] plainTextBytes, byte[] entropyBytes, string description)
    {
        // Make sure that parameters are valid.
        if (plainTextBytes == null) plainTextBytes = new byte[0];
        if (entropyBytes == null) entropyBytes = new byte[0];
        if (description == null) description = String.Empty;
        // Create BLOBs to hold data.
        DATA_BLOB plainTextBlob = new DATA_BLOB();
        DATA_BLOB cipherTextBlob = new DATA_BLOB();
        DATA_BLOB entropyBlob = new DATA_BLOB();
        // We only need prompt structure because it is a required
        // parameter.
        CRYPTPROTECT_PROMPTSTRUCT prompt =
                                  new CRYPTPROTECT_PROMPTSTRUCT();
        InitPrompt(ref prompt);
        try
        {
            // Convert plaintext bytes into a BLOB structure.
            try
            {
                InitBLOB(plainTextBytes, ref plainTextBlob);
            }
            catch (Exception ex)
            {
                throw new Exception(
                    "Cannot initialize plaintext BLOB.", ex);
            }
            // Convert entropy bytes into a BLOB structure.
            try
            {
                InitBLOB(entropyBytes, ref entropyBlob);
            }
            catch (Exception ex)
            {
                throw new Exception(
                    "Cannot initialize entropy BLOB.", ex);
            }
            // Disable any types of UI.
            int flags = CRYPTPROTECT_UI_FORBIDDEN;
            // When using machine-specific key, set up machine flag.
            if (keyType == KeyType.MachineKey)
                flags |= CRYPTPROTECT_LOCAL_MACHINE;
            // Call DPAPI to encrypt data.
            bool success = CryptProtectData(ref plainTextBlob,
                                                description,
                                            ref entropyBlob,
                                                IntPtr.Zero,
                                            ref prompt,
                                                flags,
                                            ref cipherTextBlob);
            // Check the result.
            if (!success)
            {
                // If operation failed, retrieve last Win32 error.
                int errCode = Marshal.GetLastWin32Error();
                // Win32Exception will contain error message corresponding
                // to the Windows error code.
                throw new Exception(
                    "CryptProtectData failed.", new Win32Exception(errCode));
            }
            // Allocate memory to hold ciphertext.
            byte[] cipherTextBytes = new byte[cipherTextBlob.cbData];
            // Copy ciphertext from the BLOB to a byte array.
            Marshal.Copy(cipherTextBlob.pbData,
                            cipherTextBytes,
                            0,
                            cipherTextBlob.cbData);
            // Return the result.
            return cipherTextBytes;
        }
        catch (Exception ex)
        {
            throw new Exception("DPAPI was unable to encrypt data.", ex);
        }
        // Free all memory allocated for BLOBs.
        finally
        {
            if (plainTextBlob.pbData != IntPtr.Zero)
                Marshal.FreeHGlobal(plainTextBlob.pbData);
            if (cipherTextBlob.pbData != IntPtr.Zero)
                Marshal.FreeHGlobal(cipherTextBlob.pbData);
            if (entropyBlob.pbData != IntPtr.Zero)
                Marshal.FreeHGlobal(entropyBlob.pbData);
        }
    }
    public static string Decrypt(string cipherText)
    {
        string description;
        return Decrypt(cipherText, String.Empty, out description);
    }
    public static string Decrypt(string cipherText,out string description)
    {
        return Decrypt(cipherText, String.Empty, out description);
    }
    public static string Decrypt(string cipherText,string entropy,out string description)
    {
        // Make sure that parameters are valid.
        if (entropy == null) entropy = String.Empty;
        return Encoding.UTF8.GetString(
                    Decrypt(Convert.FromBase64String(cipherText),
                                Encoding.UTF8.GetBytes(entropy),
                            out description));
    }
    public static byte[] Decrypt(byte[] cipherTextBytes,byte[] entropyBytes,out string description)
    {
        // Create BLOBs to hold data.
        DATA_BLOB plainTextBlob = new DATA_BLOB();
        DATA_BLOB cipherTextBlob = new DATA_BLOB();
        DATA_BLOB entropyBlob = new DATA_BLOB();
        // We only need prompt structure because it is a required
        // parameter.
        CRYPTPROTECT_PROMPTSTRUCT prompt =
                                  new CRYPTPROTECT_PROMPTSTRUCT();
        InitPrompt(ref prompt);
        // Initialize description string.
        description = String.Empty;
        try
        {
            // Convert ciphertext bytes into a BLOB structure.
            try
            {
                InitBLOB(cipherTextBytes, ref cipherTextBlob);
            }
            catch (Exception ex)
            {
                throw new Exception(
                    "Cannot initialize ciphertext BLOB.", ex);
            }
            // Convert entropy bytes into a BLOB structure.
            try
            {
                InitBLOB(entropyBytes, ref entropyBlob);
            }
            catch (Exception ex)
            {
                throw new Exception(
                    "Cannot initialize entropy BLOB.", ex);
            }
            // Disable any types of UI. CryptUnprotectData does not
            // mention CRYPTPROTECT_LOCAL_MACHINE flag in the list of
            // supported flags so we will not set it up.
            int flags = CRYPTPROTECT_UI_FORBIDDEN;
            // Call DPAPI to decrypt data.
            bool success = CryptUnprotectData(ref cipherTextBlob,
                                              ref description,
                                              ref entropyBlob,
                                                  IntPtr.Zero,
                                              ref prompt,
                                                  flags,
                                              ref plainTextBlob);
            // Check the result.
            if (!success)
            {
                // If operation failed, retrieve last Win32 error.
                int errCode = Marshal.GetLastWin32Error();
                // Win32Exception will contain error message corresponding
                // to the Windows error code.
                throw new Exception(
                    "CryptUnprotectData failed.", new Win32Exception(errCode));
            }
            // Allocate memory to hold plaintext.
            byte[] plainTextBytes = new byte[plainTextBlob.cbData];
            // Copy ciphertext from the BLOB to a byte array.
            Marshal.Copy(plainTextBlob.pbData,
                         plainTextBytes,
                         0,
                         plainTextBlob.cbData);
            // Return the result.
            return plainTextBytes;
        }
        catch (Exception ex)
        {
            throw new Exception("DPAPI was unable to decrypt data.", ex);
        }
        // Free all memory allocated for BLOBs.
        finally
        {
            if (plainTextBlob.pbData != IntPtr.Zero)
                Marshal.FreeHGlobal(plainTextBlob.pbData);
            if (cipherTextBlob.pbData != IntPtr.Zero)
                Marshal.FreeHGlobal(cipherTextBlob.pbData);
            if (entropyBlob.pbData != IntPtr.Zero)
                Marshal.FreeHGlobal(entropyBlob.pbData);
        }
    }
}

Расшифровка:

static void Main(string[] args)
{
  string filename = "my_chrome_passwords.html"; 
  var Writer = new StreamWriter(filename, false, Encoding.UTF8);
  string db_way = 
  Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData)
  + "/Google/Chrome/User Data/Default/Login Data"; 
  string db_field = "logins";  
  byte[] entropy = null; 
  string description;  // Неизвестный параметр
  string ConnectionString = "data source=" + db_way + 
  ";New=True;UseUTF16Encoding=True";
  var DB = new DataTable();
  string sql = string.Format("SELECT * FROM {0} {1} {2}", db_field, "", "");
  using (var connect = new SQLiteConnection(ConnectionString))
  {
    var command = new SQLiteCommand(sql, connect);
    var adapter = new SQLiteDataAdapter(command);
    adapter.Fill(DB);
    int rows = DB.Rows.Count;
    for (int i = 0; i < rows; i++)
    {
      byte[] byteArray = (byte[])DB.Rows[i][5];
      byte[] decrypted = DPAPI.Decrypt(byteArray, entropy, out description); 
      // out string description;
      string password = new UTF8Encoding(true).GetString(decrypted);
    }
 }    
}

Три Вопроса:

1 - Что делает параметр (в расшифровке ) - string description; Нужен ли он вообще?

2 - Чем отличается расшифровка класса DPAPI от простого:

public static byte[] DecryptPassword(byte[] reader)
{
   try
   {
     return ProtectedData.Unprotect(reader, null, 
     DataProtectionScope.CurrentUser);
   }
   catch (CryptographicException) { return null; }
}

3 - Обязательно ли нужно использовать DataTable ?