Selectively Connecting To Devices

[jcady92]

I have an nrf51822-mkit.

Let's say there are 2 BLE phones continuously searching for my module. Phone 1 connects and communicates with the module. The modules determines that this phone is not the correct phone, so it initiates a disconnect. When Phone 1 senses that it has been disconnected, it immediately starts scanning again for the device to connect to. But the module already knows Phone 1 is incorrect, and it would like to try to connect to Phone 2 instead. However, Phone 1 could continually keep trying to connect to the module to check if it's the correct phone.

Ideally, I would like to implement a sort of temporary blacklist. The module would check the phone, and if it's incorrect get the address of the phone, add it to a blacklist, and prohibit connections to devices that are on that blacklist. After, say, 30 seconds the device would be removed from the blacklist.

I have 2 questions:

1. How do I go about getting the address of the BLE device (phone) from my module so that it can be added to a blacklist and checked later?

2. Is it possible to prohibit certain addresses from ever connecting? Or does this have to be taken care of with logic after the connection (e.g. if the address matches a blacklisted address after connection, immediately disconnect). If the latter is the case, is it possible for one device to continuously connect and disconnect, prohibiting other devices from trying?

If anyone has any ideas on how best to implement this, I would very much appreciate them.

[David Edwin]

The white-listing will work if and only if your application on the BLE device is aware of phone 1 and phone 2. If the application is not aware of phone 2 and does not want phone 1 to connect, it cannot add phone 2 to the whitelist. This whitelist logic may not work well when adding 2 phones to the the device as known peers.

To manage the addition process: One possible method is to add an ID to the advertising packet. This ID can be a reference to the phones that have the ID should not connect so phones that do not have this ID yet will connect. This works only when you are using your own app on the phone to manage the BLE connections.

Will this work for you ?

[David Edwin]

Then I suggest that the addition process be done in a private location so there is no possibility of an attacker getting added. Once the addition has been done, use whitelisting for regular operation, manage the whitelist as suggested by @user9384 above. So during normal operation, addition of the phone will not be allowed and whitelisting will be done to manage the phones, this will prevent an attacker from maliciously connecting and blocking the device.

Will this resolve your issue ?