nRF52840 IAP (In-Application Programming). Is it possible?

[peter_100P]

I'm trying to assess the feasibility of an application using nRF52840 in a module from either Minew or Raytac. In this application, the BLE radio works stricly in Central role and the network connection is cellular, via AT commands to a Quectel modem. That's how firmware updates will enter the system, not via BLE.

Security requirements are high, and therefore firmware packages will have to be downloaded and staged into internal flash, so we can reliably validate them. Our use case doesn't fit any of your predefined "transports" in your Secure Bootloader, though, as there is no BLE, UART or USB "push". It is strictly a "pull". Are there any examples?

Oh, one more thing: Can the ECDSA public key live somewhere in flash and not be hard-coded? We need to preserve the ability to update it via our own mechanism without a DFU cycle.

[Marjeris Romero]

Hi,

There is an SPI DFU master example at the end of this DFU tutorial: https://devzone.nordicsemi.com/nordic/short-range-guides/b/software-development-kit/posts/getting-started-with-nordics-secure-dfu-bootloader

Perhaps updating through SPI will satisfy your requirements?

Regarding the public key, if you take a look at the public_key.c file (or dfu_puclick_key.c) you can find a pk[64] array. It's hardcoded in the file but can easily be change to be read from a place in flash instead of a const.

Best regards,

Marjeris

[peter_100P]

I'm afraid that's a non-starter. All traffic to and from a SPI flash is trivial to intercept and mount a MIM attack.

[Marjeris Romero]

Hi,

There is no offical support for encrypted secure DFU in the SDK.
But you might find this post by a 3rd party user helpful: https://devzone.nordicsemi.com/f/nordic-q-a/37260/adding-encryption-to-secure-dfu-sdk-v15