Using BLE to automate gate opener

[GlennEngel]

Our homeowners association has a gate which opens when a transmitter in the car is pushed. I would like to add a BLE device to the gate which would trigger the gate to open when it detects a vehicle it knows about. I imagine it consisting of two parts:

1. A beacon placed in the car. This is easy to do with the SDK.
2. A receiver of the beacon hooked to the gate electronics to trigger a relay to open the gate.

Are there existing applications that can be easily modified to support this scenario? Creating a beacon is easy enough but I wonder about support for receiving beacons using the SDK. Is this possible? Pointers to relevant documentation would be appreciated.

A related question would it possible to detect the built-in car bluetooth instead of a beacon or is the car bluetooth incompatible with BLE?

[Torsten Robitzki]

Just using a beacon to open your doors would open your system to replay attacks. I would only need a sniffer and I could just copy the signal emitted by a car.

Usually, you would add some kind of chalange. For example, receiving an encrypted random number by the gate and then sending back the decrypted random number to the gate and thus proving the knowledge of a secret key.

[GlennEngel]

This isn't a door but a gate to a neighborhood so security of communication is not critical. If someone wanted in all they have to do is wait for someone to open the gate and drive in after them instead of sitting there with a sniffer. A beacon with an encrypted payload and sequence number could be used though to secure it if needed against replay attacks so two-way wouldn't be needed. Still would like to receive beacons using the SDK though.

[endnode]

Quite obvious question: standard beacon advertises all the time with period of 20-500ms so how you would synchronize these sets of valid "encrypted" payloads? They would have many thousands of records for each key you want to keep in the memory and that still assumes that the keys would sync with gate every day (because only with 5 packets a second it makes almost half a million codes per key per day;). I'm afraid you are building simply "convenient" opener which will open to any BLE signal which goes around and that means you can very well remove the gate and solve the problem;)

[Torsten Robitzki]

In addition, while "just" receiving beacons sounds super simple: "just" establishing a connection from the gate to the car to exchange some data isn't that much harder to implement.