private extern static int GetDeviceUniqueID([In, Out] byte[] appdata,

    Private Shared Function GetDeviceUniqueID(ByVal appData As Byte(), _

GetDeviceUniqueID attempts to address these issues and to reduce applications dependency on the precious device id. Firstly GetDeviceUniqueID can be called from the trusted or untrusted code group, but the code returned is not the same as a call to KernelIoControl, its a 20 byte code not a 16 byte code. GetDeviceUniqueID takes an additional parameters of an application defined char array, and uses a one way hash to combine the real device id and the char array parameter to generate the new 20 byte code. This means that an application will always get the same 20 byte code if it calls GetDeviceUniqueID on the same device, with the same char array. It also means there is no practical way of asserting the true device id from the 20 byte key an application uses.

    // Call the GetDeviceUniqueID

    GetDeviceUniqueID(AppData, appDataSize, 1, DeviceOutput, out SizeOut);