Dim enc As System.Text.UTF8Encoding
        Dim decryptor As ICryptoTransform
 
        Dim KEY_128 As Byte() = System.Text.ASCIIEncoding.ASCII.GetBytes( _
          "KeyZumDecrypten")
        Dim IV_128 As Byte() = {234, 12, 52, 44, 214, 222, 200, 109, 2, 98, 45, _
        76, 88, 53, 23, 78}
        Dim symmetricKey As RijndaelManaged = New RijndaelManaged()
        symmetricKey.Mode = CipherMode.ECB
        enc = New System.Text.UTF8Encoding
        decryptor = symmetricKey.CreateDecryptor(KEY_128, IV_128)
 
 
        Dim cypherTextBytes As Byte() = IO.File.ReadAllBytes("DateiPfad")
        Dim memoryStream As MemoryStream = New MemoryStream(cypherTextBytes)
        Dim cryptoStream As CryptoStream = New CryptoStream(memoryStream, _
          decryptor, CryptoStreamMode.Read)
        Dim plainTextBytes(cypherTextBytes.Length) As Byte
        memoryStream.Close()
        cryptoStream.Close()
 
        System.IO.File.WriteAllBytes("DateiPfad", plainTextBytes)

Dim decryptedByteCount As Integer = cryptoStream.Read(plainTextBytes, 0, _
  plainTextBytes.Length)