Maybe I'm wrong, but there's currently no sort of authentication protocol for devices in USB, right? I (and I think jimrandomh too) was thinking of USB as-is. Something that OSes can do right now without having to wait for whoever controls the USB spec. As it is, how can an OS know that the mouse it sees on waking up is the same mouse that was connected before it slept or powered off? I don't think there's any sort of cryptographic authentication specified for USB devices.