nRF52811 OTA/DFU Feasibility

RE: nRF52811 OTA/DFU Feasibility

Vidar Berg — Tue, 26 Aug 2025 14:18:32 GMT

They can initiate the DFU process by reusing the init command from a valid update (an init command signed with your key). They will not be able to update to another firmware, but they can use this to erase the current application.

[quote user="Purvesh patel"]However, I am wondering about other possibilities — for example, what happens if the firmware data itself gets corrupted during transfer?[/quote]

The integrity of the received FW is validated against the hash in the init command. The bootloader will fall back to dfu mode if the validation fails.

RE: nRF52811 OTA/DFU Feasibility

Purvesh patel — Tue, 26 Aug 2025 12:43:34 GMT

Hello Vidar,

text:

// <q> NRF_DFU_SINGLE_BANK_APP_UPDATES - Place the application and the SoftDevice directly where they are supposed to be.

// <i> Note that this creates security concerns when signing and version checks
// <i> are enabled. An attacker will be able to delete (but not replace)
// <i> the current app or SoftDevice without knowing the signature key.

#ifndef NRF_DFU_SINGLE_BANK_APP_UPDATES
#define NRF_DFU_SINGLE_BANK_APP_UPDATES 1
#endif

Testing Results [currently testing for nrf52840 on nrf52840 dk with old nrf5sdk]

Wrongly signed file test:

Transfer immediately stopped with log: [DFU] Remote DFU error: invalid object
Upon reset/timeout, device behaves normally
Invalid Object error with OTA DFU using both example and self generated packages. points it is due to key

Questions

Security concern confirmation: Can you confirm the actual security risk? Based on my testing, wrongly signed files are rejected immediately - I cannot successfully perform the attack described in the warning.

Also

[quote userid="147580" url="~/f/nordic-q-a/123897/nrf52811-ota-dfu-feasibility"]3) Single slot DFU reliability - Recovery mechanism If it will be single slot DFU, what happens if there's an error during firmware transfer (power loss, connection drop, corrupted data)? Can the device be recovered thereafter using OTA, or would it require physical access/JTAG programming?[/quote]

I tried disconnecting my Bluetooth connection midway during the DFU process, and I observed that the device gets stuck in DFU mode, advertising as DFUTARG. It can only be recovered by performing a successful OTA update.

However, I am wondering about other possibilities — for example, what happens if the firmware data itself gets corrupted during transfer?

Can you confirm me this two things?

Testing for nr52811 on nr52840 dk

I got the same error as this

peer_manager_pds: Could not initialize flash storage. fds_init() returned 0x860A

but i can't access many links given in the solution

RE: nRF52811 OTA/DFU Feasibility

Vidar Berg — Mon, 25 Aug 2025 11:32:23 GMT

Hello,

Yes, OTA dfu is supported on the nrf52811 as long as the application is not too big. But if you have already developed the application with the nRF Connect SDK but not the hardware, it should be easy to transition to the nRF54L series devices, which offer more memory and performance at a lower cost.

[quote user=""]Simple BLE blinky (nRF5 SDK): 122 kB of 192 kB (63.6%)[/quote]

This is including the Softdevice which won't be upgradeable with this setup. To get the size of the app you must substract 122 with the size of the softdevice you've selected.