Bonding. Why ltk changed at every reconnection?

RE: Bonding. Why ltk changed at every reconnection?

Petter Myhre — Wed, 30 Sep 2015 12:12:59 GMT

It is a bit strange that you get BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION for the Nexus 7 if you turn off Bluetooth in settings, but I don't think this is the root of the issue. If you can, please do a sniffer trace.

RE: Bonding. Why ltk changed at every reconnection?

Petter Myhre — Wed, 30 Sep 2015 12:11:14 GMT

I mean on the air sniffing yes. It would be very helpful, thank you.

RE: Bonding. Why ltk changed at every reconnection?

Valer_I — Wed, 30 Sep 2015 11:24:12 GMT

I tested on Win8.1 and it works, on Nexus7 doesn't. The test case was the next:

bonding
disconnection from host by switching off bluetooth or removing the BLE dongle.
On periperal wthite list become working and after switching on bluetooth on central, it connects and in one case rebonds with new LTK, in other case using previous bond.

When I receive BLE_GAP_EVT_DISCONNECTED the ble_evt->evt.gap_evt.params.disconnected.reason is BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION for Nexus7 and BLE_HCI_CONNECTION_TIMEOUT for Win8.1. Could this parameter be connected with described issue?

I think I found. In Android code each time I connected the method called

device.createBond();

Now it changed to and seems to work properly, but it not always define bond status correctly(((

if (device.getBondState() != BluetoothDevice.BOND_BONDED) {
    device.createBond();
}

RE: Bonding. Why ltk changed at every reconnection?

Valer_I — Wed, 30 Sep 2015 10:59:31 GMT

Sorry for late responce. I have made some experiments. My issue connected with loss of bond information on master or slave. If bond saved and loaded correctly I receive BLE_GAP_EVT_SEC_INFO_REQUEST. About pairing encryption request, for Windows 8.1 it seems that I can't make any impact on bonding process so I can't generate this request. If you mean air sniffing, I need some data about this request first.

RE: Bonding. Why ltk changed at every reconnection?

Petter Myhre — Fri, 25 Sep 2015 14:15:40 GMT

The peripheral application will receive the BLE_GAP_EVT_SEC_INFO_REQUEST event if it gets a pairing encryption request, which the central sends if the central application calls sd_ble_gap_encrypt(). Is your central application calling this?

RE: Bonding. Why ltk changed at every reconnection?

Valer_I — Fri, 25 Sep 2015 08:51:23 GMT

Both S110 and S130 were tried on nRF51422QFAAE0. I neither use SDK nor Device manager. I interact with sotdevice only within sd_ble_... functions. What should I see if sniff the air? In debug I ablle to see all BLE events to compare with flowcharts from mentioned above document references. As central do not sent the BLE_GAP_EVT_SEC_INFO_REQUEST after connection may I suppose that it doesn't remember the bond?

RE: Bonding. Why ltk changed at every reconnection?

Petter Myhre — Thu, 24 Sep 2015 12:54:43 GMT

What SDK and SoftDevice version are you using? Are you using the device manager? What is your central device? Have you tried to sniff to see what is happening on air?