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When do encryption keys exchange?

MC

I have a problem with bonding with a static passkey. I have some sensors, which have a static passkey hardcoded in them. If I want to bond with them, I have to provide this passkey from my custom central app, which uses s120 and SDK 8.1.0. For the past few days I wasn't able to make a successfull bond, because I keep getting BLE_GAP_SEC_STATUS_AUTH_REQ from the sensor. I can't find much information on what to do in this case. I can bond with MCP just fine.

I compared log file from MCP and sniffer trace from my central bonding attempt and they are different in one very impotant aspect. MCP exchanges keys and encrypts the connection before trying to authenticate the link. Default behavioral of the device manage in SDK 8.1.0 is not the same. If I call dm_security_setup_req it only forces authentication without previous key exchange. This is why authentication fails. If I go into debug mode, I can see that keys are always 0. Does anyone have any suggestions about this matter? Are there any examples that mimic MCP behavioral?

Edit: added trace logs for windows phone, s120 and MCP log file, all done with the same sensor (which uses TI stack).

Windows phone pairing attempt: windows_pairing_with_adv.pcapng

S120 pairing attempt: s120_central_pairing.pcapng

MCP log file: log.txt

Android bonding attempt: android_bonding.pcapng

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    First, you will need a peripheral, which has a static passkey hardcoded in the code. In my case, I have "000000". The sensors I have, require this passkey at bonding (pairing) procedure. Second, use some example code, lets say s120 multilink central example. Please use SDK 8.1.0. Then, connect to the peripheral and inside the client_handling_create function, call the function dm_security_setup_req.

    After that, you should get an event from DM DM_EVT_SECURITY_SETUP_COMPLETE in main() with event_result 0x83. This comes from the fact, that dm_security_setup_req function forces authentication for unbonded devices by calling initiate_security_request. Because authentication function requires encryption keys to be available, it will always fail, given the fact that link hasn't been encrypted. Edit: added PNGs to my main question for clarification of the problem.

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    First, you will need a peripheral, which has a static passkey hardcoded in the code. In my case, I have "000000". The sensors I have, require this passkey at bonding (pairing) procedure. Second, use some example code, lets say s120 multilink central example. Please use SDK 8.1.0. Then, connect to the peripheral and inside the client_handling_create function, call the function dm_security_setup_req.

    After that, you should get an event from DM DM_EVT_SECURITY_SETUP_COMPLETE in main() with event_result 0x83. This comes from the fact, that dm_security_setup_req function forces authentication for unbonded devices by calling initiate_security_request. Because authentication function requires encryption keys to be available, it will always fail, given the fact that link hasn't been encrypted. Edit: added PNGs to my main question for clarification of the problem.

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