[NRF52840 - pc-ble-driver-py] - Disconnection/reconnection issue

RE: [NRF52840 - pc-ble-driver-py] - Disconnection/reconnection issue

mattfavre — Fri, 28 Feb 2020 08:58:55 GMT

Hi Christophe@,

Thanks for the reply, it worked for me.

Matt

RE: [NRF52840 - pc-ble-driver-py] - Disconnection/reconnection issue

Christophe@ — Sat, 22 Feb 2020 13:54:56 GMT

Hi Matt,

After bonding, you have to get the keyset. In ble_adapter.py, I used the code of authenticate function to write my code:

keyset = BLEGapSecKeyset.from_c(self.adapter.driver._keyset)

Then, from keyset, you can get ediv, rand, ltk (ble_driver.py):

self.ediv = keyset.keys_own.enc_key.master_id.ediv
self.rand = keyset.keys_own.enc_key.master_id.rand
self.ltk = keyset.keys_own.enc_key.enc_info.ltk

You can proceed to encryption with:

self.adapter.encrypt(self.conn_handle, self.ediv, self.rand, self.ltk)

After a disconnection, when you reconnect, you have to call encrypt again.

I hope that will help you.

Regards,

Christophe

RE: [NRF52840 - pc-ble-driver-py] - Disconnection/reconnection issue

mattfavre — Wed, 19 Feb 2020 08:26:40 GMT

Hi Christophe@,

Your question is very relevant.

Could you post an example of your final code?

Regards,

Matt

RE: [NRF52840 - pc-ble-driver-py] - Disconnection/reconnection issue

tesc — Thu, 31 Oct 2019 12:53:14 GMT

Hi,

I am happy to hear that you solved the issue, and wish you good luck with the rest of the project.

Regards,
Terje

RE: [NRF52840 - pc-ble-driver-py] - Disconnection/reconnection issue

Christophe@ — Wed, 30 Oct 2019 15:57:47 GMT

Hello Terje,

I succeeded to do this reconnection. I got ediv, rand and ltk from keyset using last part of code of method authenticate in ble_adapter.py and I used encrypt method to establish encryption.

That issue is fixed. Thanks again for your support.

Regards,
Christophe

RE: [NRF52840 - pc-ble-driver-py] - Disconnection/reconnection issue

tesc — Thu, 17 Oct 2019 16:13:49 GMT

Hi,

You need to add procedures for reestablishing encryption, using stored keys (ediv, rand, LTK) for the bond. I.e. Encryption Establishment using stored keys. Either always after connection, or when you get a security request as in Security Request Reception.

The keys can be fetched from the SoftDevice as part of the bonding procedure, from the [in,out] parameter p_sec_keyset in sd_ble_gap_sec_params_reply(). See the API documentation for sd_ble_gap_sec_params_reply() for details.

Regards,
Terje

RE: [NRF52840 - pc-ble-driver-py] - Disconnection/reconnection issue

Christophe@ — Tue, 15 Oct 2019 14:42:50 GMT

Hello Terje,

Thank you for your answer. There are a lot of workflows available in Central Security Procedures. Which one should I use to fit my needs?

Currently, I use Bonding: Passkey Entry, User Inputs on Central or OOB. Can I keep it or should I replace it with another procedure?

Regards,
Christophe

RE: [NRF52840 - pc-ble-driver-py] - Disconnection/reconnection issue

tesc — Mon, 14 Oct 2019 10:48:22 GMT

Hi,

pc-ble-criver (and pc-ble-driver-py) is serialization of the SoftDevice, and the SoftDevice does not store bonding data internally. That means, in order to keep the bond on the pc side you must store that data yourself. This is what for instance the Peer Manager library in the nRF5 SDK does. See e.g. the Central Security Procedures in the SoftDevice API documentation.

Regards,
Terje