LESC "Just Works" Reconnection Issues

[Tom Jimenez]

SDK: NCS 1.7.1.

Based on: Peripheral UART example

Central: nRF Dongle

Peripheral: nRF52832

Hi,

I am running into an issue using the "Just Works" pairing method when attempting to reconnect after successfully pairing and bonding. I modified the "Peripheral_UART" example based on the following link https://devzone.nordicsemi.com/f/nordic-q-a/77391/allow-lesc-just-works-pairing-bonding-with-nrf-connect-sdk-zephyr-after-pressing-button/336031#336031 and was successful in pairing and bonding on the initial connection. Upon reconnection, the connection is dropped, and the following output is seen using puTTy: 

E: SMP Timeout
Security failed: DE:56:61:DF:19:86 (random) level 1 err 8
Pairing failed conn: DE:56:61:DF:19:86 (random), reason 8

Reason 8 refers to "BT_SMP_ERR_UNSPECIFIED" so that doesn't give me much information.

I used an Ellisys Sniffer and I was able to see that the connection is dropped after the "LLCP Encryption Start" event when reconnecting.

Any advice would be appreciated!

Best,

Tom

[ovrebekk]

Hi Tom

Do you know if the bonding data is properly stored and recalled when you reconnect the already bonded connection?

Typically what happens after the encryption is started is that you need to reconfigure the encryption data that was stored during the bonding phase. 

I haven't tested LESC pairing in NCS myself yet, but I will check with my colleagues tomorrow if there is anything in particular to look out for. 

Best regards
Torbjørn

[Tom Jimenez]

Hello Torbjørn,

Yes, the bonding data is properly stored. 

Upon doing some more testing, the example works with an iPhone and an Android as the central. The link is correctly re-encrypted upon reconnection. 

It seems as if the nRF dongle is the cause of the issue that we have been seeing. The dongle has the latest firmware on it and we tested multiple dongles with the same result.

Best,

Tom

[ovrebekk]

Hi Tom

That is interesting. 

By 'nRF Dongle', do you mean this one?

Which application are you using on the central side to control the dongle?

Best regards
Torbjørn

[Tom Jimenez]

Hello Torbjørn,

Yes, that is the dongle that I am referring to.

I am using an unmodified firmware provided by the nRF Connect for Desktop application.

Thank you,

Tom

[ovrebekk]

Hi Tom

Thanks for the clarification. 

Would you be able to share your code with me so I can try to reproduce the problem here?

I can make the case private, if you don't want to share your code in a public ticket. 

Best regards
Torbjørn