IOCTL_HAL_GET_HWENTROPY - should this be unique to each hardware?

Hi,
I need to supply IOCTL_HAL_GET_HWENTROPY.
should this be unique to the device, or can it be a function of some
device property such as "Available free memory" ? etc
Thanks in advance!!!!
Rags

dangrif
Fri Nov 04 19:30:24 CST 2005

Hello,

IOCTL_HAL_GET_HWENTROPY should return a 64-bit random number that is unique
to the device. This means that the hardware must provide some form of
unique identifier that varies from device to device.

The value returned from a call to IOCTL_HAL_GET_HWENTROPY should never
change for a particular device. So, while your idea of using some other
random property of the system (such as the currently available free memory)
is a good one, it doesn't match the intended use of this IOCTL. If your
device's hardware does not provide a unique identifier, this IOCTL should
return FALSE and set the last error to ERROR_NOT_SUPPORTED.

Dan
dangrif <at> microsoft <dot> com