How to solve the problem "Encrypted packet decrypted incorrectly (bad MIC)" ?

[lupin]

Hello, I'm using nrf sniffer and wireshark to capture my BLE device's packets.

I'm using nRF52840 dongle with firmware of the "nrf_sniffer_for_bluetooth_le_3.1.0_7cc811f".

My device set as non-secure connection mode and non-mitm protection to be decrypted with the sniffer.

I checked the packets are decrypted successfully without entering passkey with the settings at 1 month ago.

But when I try today, the packet is not decrypted with "Encrypted packet decrypted incorrectly (bad MIC)" unless entering passkey.

It's very strange. Any check points for this?

Thanks,

Calvin

[Sigurd]

Hi,

Could be that the peer you are connecting to now is requesting a higher security level.

Another thing you can try, is to delete the bond information on both devices, and then bond again while the sniffer is running/sniffing the connection when the pairing/bonding happens.

[lupin]

The secure connection flag is false and mitm flag is false in the pairing response packet.

Isn't that sufficient as a condition for not having to enter a passkey?

Could you check the attached packet log?

decryption_mic.pcapng

Thanks,

Calvin

[Sigurd]

Seems like your device have a display,

Try setting this, and see if you are able to decrypted the packets:

#define SEC_PARAM_IO_CAPABILITIES           BLE_GAP_IO_CAPS_NONE                    /**< No I/O capabilities. */

[Jema]

I've the same issue ... and my remote has a display ...

Where I should add this line:

#define SEC_PARAM_IO_CAPABILITIES           BLE_GAP_IO_CAPS_NONE                    /**< No I/O capabilities. */

Thanks

[Sigurd]

If your application have added the Peer Manager, you typically have these defines at top of main.c , see e.g ble_app_hrs example.

If you are having problems with this, please open a new case. This case is ~3 years old.

PS: If this is a new product you are making, I recommend using the nRF Connect SDK https://www.nordicsemi.com/Products/Development-software/nrf-connect-sdk