Help in decrypting BLE packets using nrf52840 USB dongle

[anusha_14]

Hello Nordic support,

I would like to understand how I can decrypt the packets that is using Legacy passkey pairing. Here is the BLE sniffer log, where I selected Legacy Passkey and provided the key used during pairing process. However, I still do not see decrypted packets and when the BLE central device connects to BLE peripheral, I can only see MTU request exchange and none of the other packets.

File - PairingWithLegacyPassKeYsniffing.pcapng

In the shared log, packet 1291 shows the pairing request:

Packet 2454 shows an instance where BLE central is connecting to peripheral but does not any BLE communication between them, except for MTU request:

Can you please let me know the process to follow to successfully decrypt packets using nrf52840 BLE dongle?

Regards,

Anusha

[Vidar Berg]

Hello Anusha,

Could you provide some details about your setup and explain why you’re trying to sniff this connection? I assume you’re troubleshooting a specific issue. I reviewed the trace and the sniffer appears to only be receiving every other connection event for some reason. It's also missing the key exchange so it doesn't receive the long term encryption key (LTK) needed to decrypt subsequent connections were this key will be used. 

Best regards,

Vidar