Hi everyone, I am facing an issue when modifying the peripheral_nfc_pairing example. Due to hardware limitations, my device cannot integrate an NFC antenna. Instead, I plan to use an external NFC tag attached to the device. When a phone (Central) taps the NFC tag, it should trigger the pairing process. My idea is to fix some parameters (e.g., TK) in the OOB record and write them into the NFC tag. The goal is to achieve Legacy OOB Pairing with Security Level 3 . Currently, I am testing on an nRF5340 DK with NFC antenna (not yet using an external NFC tag), running nRF Connect SDK 2.9.1. However, after applying my modifications, the pairing only results in Security Level 2 . My modifications: I use a fixed tk_value instead of generating random TK. Replaced all usage of tk_value with tk_value_fixed , including in the record payload. In the OOB record payload, I did not provide le_sc_data , to enforce Legacy Pairing. Observed results: The connection only achieves Security Level 2, and it seems the OOB data is not used. In the pairing_accept callback, the SC flag in auth_req is still set, and oob_data_flag = 0. The auth_oob_request callback is never called . Questions: Am I misunderstanding the OOB mechanism, or am I going in the wrong direction? Is the idea of using an NFC tag with fixed TK for Legacy OOB Pairing feasible? Any ideas or suggestions would be greatly appreciated. Thank you very much! TRANSLATE with x English Arabic Hebrew Polish Bulgarian Hindi Portuguese Catalan Hmong Daw Romanian Chinese Simplified Hungarian Russian Chinese Traditional Indonesian Slovak Czech Italian Slovenian Danish Japanese Spanish Dutch Klingon Swedish English Korean Thai Estonian Latvian Turkish Finnish Lithuanian Ukrainian French Malay Urdu German Maltese Vietnamese Greek Norwegian Welsh Haitian Creole Persian TRANSLATE with COPY THE URL BELOW Back EMBED THE SNIPPET BELOW IN YOUR SITE Enable collaborative features and customize widget: Bing Webmaster Portal Back

Legacy Pairing using OOB NFC

Hi everyone,

I am facing an issue when modifying the peripheral_nfc_pairing example.

Due to hardware limitations, my device cannot integrate an NFC antenna. Instead, I plan to use an external NFC tag attached to the device. When a phone (Central) taps the NFC tag, it should trigger the pairing process.

My idea is to fix some parameters (e.g., TK) in the OOB record and write them into the NFC tag. The goal is to achieve Legacy OOB Pairing with Security Level 3.

Currently, I am testing on an nRF5340 DK with NFC antenna (not yet using an external NFC tag), running nRF Connect SDK 2.9.1.
However, after applying my modifications, the pairing only results in Security Level 2.

My modifications:

I use a fixed tk_value instead of generating random TK.
Replaced all usage of tk_value with tk_value_fixed, including in the record payload.
In the OOB record payload, I did not provide le_sc_data, to enforce Legacy Pairing.

Observed results:

The connection only achieves Security Level 2, and it seems the OOB data is not used.
In the pairing_accept callback, the SC flag in auth_req is still set, and oob_data_flag = 0.
The auth_oob_request callback is never called.

Questions:

Am I misunderstanding the OOB mechanism, or am I going in the wrong direction?
Is the idea of using an NFC tag with fixed TK for Legacy OOB Pairing feasible?

Any ideas or suggestions would be greatly appreciated.
Thank you very much!

0 Vidar Berg 7 months ago

Hello,

Are you sure phone supports OOB pairing (i.e. did it work before you made these changes)? iOS doesn't implement support for OOB pairing, and support on Android varies depending on the vendor and device model.

Best regards,

Vidar
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0 nguyen.thnhkhoi 7 months ago in reply to Vidar Berg

Yes, it worked before I made these changes (My phone is running Android 13, it does support Bluetooth 5.1). Before modifying the example, it completely established the LESC Level 4.

Thank you for your attention.

0 Vidar Berg 7 months ago in reply to nguyen.thnhkhoi

Support for NFC pairing can vary between different models even if the run the same Android version. That said, I'm not sure why SC OOB pairing seemingly works but not legacy OOB doesn't. Maybe the phone supports one but not the other. One of the differences between SC OOB and legacy oob pairing is that for legacy pairing the initiator (phone in this case) must set the OOB flag for OOB data to be used (Ref. 2.3.5.1. Selecting key generation method).
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