Unexpected indicated connection security with connectivity firmware

[Adrian Eggenberger]

Hi

I've implemented a BLE peripheral based on the SDK11. For bonding i'm using the new peer manager. If the code runs on a nRF51 DK the bonding works properly. After the connection has been established a pin code may be inserted on the smart device. Afterwards the connection security reaches mode 1/level 3 with encryption key size of 16. On reconnect the connection security reaches again the Mode 1/Level 3 level without entering a pin. So far so good.

If the BLE peripheral code runs on a host system and uses serialization to communicate with a nRF51 DK with connectivity firmware the behavior is different.

The bonding still works properly, but after a reconnect the security level indicated by the BLE_GAP_EVT_CONN_SEC_UPDATE is Mode 1/Level 2 with Keysize 8. The strange thing is, that accessing a characteristic with security level Mode 1/ Level 3 works properly. I assume that the connection security is in the correct mode/level, but the indicated mode/level is wrong.

Any idea what can cause an invalid indicated connection security mode?

Regards Adrian

[Petter Myhre]

I think your assumption is correct. I will investigate. You could also try putting a breakpoint in the nRF51 and check the BLE_GAP_EVT_CONN_SEC_UPDATE event, before it is relayed.

[Adrian Eggenberger]

I actually added some code in the connectvity firmware to verify if the event from the softdevice contains the unexpected values or if it's a serialisation/deserialisation problem. That was my first guess, but the event coming from the softdevice in the connectivity firmware alredy contains the invalid values.

If I should test something to help to investigate the issue please ask.

[Petter Myhre]

I see. Do you get the correct security level with the BLE_GAP_EVT_CONN_SEC_UPDATE event when you do the initial bonding? Would it be possible to share your project? If it is confidential or secret you can do it privately through your MyPage at www.nordicsemi.com

[Adrian Eggenberger]

After the initial bonding the security mode is correct. After a disconnect and reconnect the security mode is invalid. I'll check if i can share the project or parts of it to reproduce. What parts of the project do you need? Host, Connectivity or Both?

[Petter Myhre]

Ok. Thanks. Both if you have changed the connectivity source code.