[nRF Connect SDK] How to recover BLE connection when BLE lost its pairing?

RE: [nRF Connect SDK] How to recover BLE connection when BLE lost its pairing?

Simonr — Mon, 17 Jul 2023 11:49:47 GMT

Einar is on vacation, so I have taken over this case in the meantime. Let me know if you require any further action points from our side.

Best regards,

Simon

RE: [nRF Connect SDK] How to recover BLE connection when BLE lost its pairing?

Tim Hwang — Wed, 12 Jul 2023 08:29:41 GMT

We could not determine official comments to my customer about this issue yet.
This case can be reopen someday.

Thank you!

RE: [nRF Connect SDK] How to recover BLE connection when BLE lost its pairing?

Tim Hwang — Thu, 06 Jul 2023 08:44:03 GMT

Thanks for updating. let me have to think how I tell my boss.

RE: [nRF Connect SDK] How to recover BLE connection when BLE lost its pairing?

Einar Thorsrud — Thu, 06 Jul 2023 08:41:18 GMT

I understand you point, but the only proper way to work around this without telling the customer to delete the bond is to reserve more space for bonding (so you don't have to delete bonds that often / perhaps never). This is generally how things work with all Bluetooth devices that use bonding.

There is one other potential approach though. That is to change the address of the nRF, so that the Windows machine will see it as a new device. But this will also cause problems for other already computers bonded with this device where both still have the bond, because it will not see the nRF as the same device anymore, and those bonds will also be useless in this case.

To sum up, this is not a problem specific to the nRF, rather the limitation you are seeing here is an intentional security feature. On the nRF it is configurable, on Windows/iOS/Android, it is not.

RE: [nRF Connect SDK] How to recover BLE connection when BLE lost its pairing?

Tim Hwang — Thu, 06 Jul 2023 08:28:37 GMT

I agree with your opinion.
But Nordic has limit of max bonding due to memory. Nordic cannot store all the host it paired.

If Nordic already removed old pairing of win 10, But win 10 might have pairing information.
You and I understand this situation, but my customer directly cannot recognize it.
They just can report it as issue.

So I'm asking you if we may have solution to prevent it.
If Nordic does not have pairing information, Nordic can let win 10 know pairing should be initiated again.
But in my study, Nordic just send disconnection to win 10.

If we can prepare solution, my customer will experience better service. and we can sell more product.
Thanks.

RE: [nRF Connect SDK] How to recover BLE connection when BLE lost its pairing?

Einar Thorsrud — Thu, 06 Jul 2023 08:18:15 GMT

Hi,

I was unsuccessfully trying to reproduce this, but now I wonder if I misread the original issue. Did you remove the pairing on Windows or the nRF? If you remove the pairing on the nRF then you must also remove the pairing on Windows in order to proceed. Windows (like iOS and Android) will not allow you to replace an existing bond. (This is because it is a security risk as an attacker can spoof the address of the bonded device and replace the bond).

RE: [nRF Connect SDK] How to recover BLE connection when BLE lost its pairing?

Tim Hwang — Tue, 04 Jul 2023 01:34:57 GMT

devzone.nordicsemi.com/.../0704_5F00_log.txt

Thanks for updating. But it still remain disconnected.(nothing different)
Attached log is about "CONFIG_BT_SMP_ALLOW_UNAUTH_OVERWRITE=y."

BTW I add those two lines to initiate pairing process again when connected.

bt_set_bondable(true);
bt_conn_set_security(conn, BT_SECURITY_L4);
It was not effective for me. "security failed" log is added.

Do you have another idea?

[Log]
Security failed: 14:AB:C5:AE:75:17 (public) level 1 err 2

RE: [nRF Connect SDK] How to recover BLE connection when BLE lost its pairing?

Einar Thorsrud — Mon, 03 Jul 2023 12:15:16 GMT

Hi,

If the peer lost the bonding information, you either need to delete the bond on the nRF, or allow an existing bond to be replaced. The latter can be achieved by using CONFIG_BT_SMP_ALLOW_UNAUTH_OVERWRITE=y.