Pregenerating Bluetooth link keys

In my project, there will be about 500 Bluetooth devices installed over the city and about 20 PDAs used to update these devices.

The devices should be not be visible to anything except the PDAs and I'd like to avoid the troubles or pairing each device to each PDA.

Is there any way to pregenerate 10,000 link keys (for each device-PDA pair), knowing their device addresses, so that link keys for each of the devices could be uploaded all at once during the firmware upload p开发者_如何学运维rocess?

define a shared secret and use the mac-addresses as salt. with this, you are able to generate a key, which is known on both systems.

or something like that :)

pseudo:

key = int(private part (shared secret) + public part (mac-address))