An Even Simpler Smartphone Garage Door Opener
posted Jun 15th 2011 6:06am by Nick Schulzefiled under: cellphones hacks, classic hacks

We have seen smartphone garage door openers in the past, but [Lou's] Hack is beautiful in its simplicity. His door opener tackles the problem without using computers, Arduinos, wireless modules or even any smartphone based applications. For this project all that is needed is a Bluetooth headset and a single transistor. The door opener uses the Samsung HM1100 Bluetooth headset, which [Lou] has done significant testing on to show that his creation is quite secure and will not open the door unexpectedly.
When this headset connects to a phone it produces a beep from the earbud, so [Lou] removed the speaker and replaced it with a transistor. Now he can use the voltage spike produced by the amplifier before the beep as his switching signal. By wiring the transistor in parallel with the door button inside his garage he is able to open the door wirelessly by connecting then right away disconnecting from the headset. This setup is apparently perfectly secure as the only way to initially link your phone with the headset is to be inside the garage. Check out the video after the break for build instructions and a demonstration.






I’d think that hacking it would be a pretty simple matter of sniffing the Bluetooth pairing as it happens, and looking at the BT Mac Address of the “trusted” phone, and spoofing it with your own device; my understanding is that the pairing profile on most Bluetooth audio devices is actually pretty simplistic/insecure, but I could be wrong.
Another problem would be approaching this while on a call — with most phones, when you pair a Bluetooth headset, it will “hijack” the call, taking precedence over the built-in microphone/speaker until you disable in software again. Not a huge deal if you see it coming, more of a minor annoyance.
Both of those things being said, it’s a nice, elegant solution. The security concerns are really unnecessary — if an attacker was sophisticated enough to do that kind of Bluetooth hackery, they’re probably plenty capable with a set of lock picks. Like any lock, it’s more of a deterrent than an absolute defense; it’s simply important to recognize the weaknesses in your system so you can be better suited to strengthen them if it’s found necessary.