nRF Sniffer: J-Link and Decryption Questions

[Mara]

Hi all,

Our company needs a BLE Sniffer and I've stopped my attention on nRF52 DK board. As stated in its documentation a SEGGER J-Link is necessary to upload the nrf sniffer firmware.

We do not have exactly SEGGER j-Link product but do have a SiLabs Ember Debug Adapter ISA3 that is said to support SEGGER J-Link (www.silabs.com/.../how_to_use_j-linkde-yiel). Do you think it can be used to flash the firmware? SEGGER J-Link is not cheap and we would use it only for flashing the sniffer firmware. We are developing at a higher protocol level and are not so experienced in these tools.

I have a question regarding the sniffer's capability of decrypting packets: which versions of the Bluetooth Specification does it support: are Secure Connections supported? Does it use Man-in-the-middle approach to decrypt as the Bluetooth Spec states that just works is protected from passive eavesdropping.

[Einar Thorsrud]

Hi,

I think there is a misunderstanding here. You need the SEGGER J-Link software, but no additional HW. This is because the nRF52 DK has an onboard SEGGER J-Link debugger.

LE Secure connection packets cannot be decrypted. Decryption works with legacy pairing, since the encryption key is transmitted over the air when pairing. This is not the case with LE Secure connections, since this use a Diffie–Hellman key exchange.

[Mara]

Hi Einar,

Thank you for the immediate response.

That's exactly what I was afraid of but as I did not see a note in the docs that Legacy Pairing only is supported I hoped you've used some trick. Anyway, thanks a lot for making this clear.