BLE Sniffer, encrypted packet decrypted incorrectly (bad MIC)

[wojci]

I'm using https://nsscprodmedia.blob.core.windows.net/prod/software-and-other-downloads/desktop-software/nrf-sniffer/sw/nrf_sniffer_for_bluetooth_le_4.1.1.zip with a nRF52840 Dongle. This combination appears to be supported.

I'm using Just Works pairing.

I'm able to sniff the BLE advertisements/connection between me PC and phone, but not between same phone and another device.

The sniffer is unable to follow the connection (between app and device) after the phone connects to the device and shows "encrypted packet decrypted incorrectly (bad MIC)".

Should I attach the captured logs.

[Karl Ylvisaker]

Hello,

I'm able to sniff the BLE advertisements/connection between me PC and phone, but not between same phone and another device.

The sniffer is unable to follow the connection (between app and device) after the phone connects to the device and shows "encrypted packet decrypted incorrectly (bad MIC)".

Is the phone and other device already paired when you attempt this?

I would recommend taking a look through the Sniffer Common Usage scenarios in the documentation, to see how you can sniff the communication between devices that use pairing.

Best regards,
Karl

[wojci]

Thank you for your help.

On Android there is no pairing. I managed to capture one log but it took a number of tries.

On iphone I deleted old pairings (I assumed that justworks would not require this ..) and managed to capture a log after some retries.

The sniffer often stops sending data to my PC while I'm sniffing a connection between two devices.

So while it works it takes some effort .. retries to sniff a connection between two LE devices.

I'm using the provided Python example to find advertisement packets from a specific device and then sniff a connection.

[Karl Ylvisaker]

Hello,

wojci said:

Thank you for your help.

No problem at all, I am happy to help! :) 

wojci said:

The sniffer often stops sending data to my PC while I'm sniffing a connection between two devices.

Please check your Windows device manager properties for the COM port you are using to see if it has power saving enabled, as this could be what is closing stopping the sniffer.

wojci said:

So while it works it takes some effort .. retries to sniff a connection between two LE devices.

I'm glad to hear that you've got it up and running now! 

Please do not hesitate to open another ticket if you should encounter any other issues or questions in the future.

Good luck with your developing! :)

Best regards,
Karl