Random hardware unique key

This sample writes random hardware unique keys (HUKs) to the Key Management Unit (KMU), when available, or to the relevant flash memory page, when the KMU is not present.

Requirements

The sample supports the following development kits:

Hardware platforms

PCA

Board name

Build target

nRF9160 DK

PCA10090

nrf9160dk_nrf9160

nrf9160dk_nrf9160

nRF5340 DK

PCA10095

nrf5340dk_nrf5340

nrf5340dk_nrf5340_cpuapp

nRF52840 DK

PCA10056

nrf52840dk_nrf52840

nrf52840dk_nrf52840

nRF21540 DK

PCA10112

nrf21540dk_nrf52840

nrf21540dk_nrf52840

Overview

When using the Hardware unique key library together with the nRF Secure Immutable Bootloader, you must provision a hardware unique key for the bootloader into the relevant KMU slot or flash memory page.

To provision the HUKs, build and run this sample before programming the bootloader and application. It will save the HUKs in the device.

Configuration

See Configuring your application for information about how to permanently or temporarily change the configuration.

FEM support

You can add support for the nRF21540 front-end module to this sample by using one of the following options, depending on your hardware:

  • Build the sample for one board that contains the nRF21540 FEM, such as nrf21540dk_nrf52840.

  • Manually create a devicetree overlay file that describes how FEM is connected to the nRF5 SoC in your device. See Set devicetree overlays for different ways of adding the overlay file.

  • Provide nRF21540 FEM capabilities by using a shield, for example the nRF21540 EK shield that is available in the nRF Connect SDK. In this case, build the project for a board connected to the shield you are using with an appropriate variable included in the build command, for example SHIELD=nrf21540_ek. This variable instructs the build system to append the appropriate devicetree overlay file.

    To build the sample in the nRF Connect for VS Code IDE for an nRF52840 DK with the nRF21540 EK attached, add the shield variable in the build configuration’s Extra CMake arguments and rebuild the build configuration. For example: -DSHIELD=nrf21540_ek.

    See nRF Connect for VS Code extension pack documentation for more information.

    See Programming nRF21540 EK for information about how to program when you are using a board with a network core, for example nRF5340 DK.

Each of these options adds the description of the nRF21540 FEM to the devicetree. See Working with RF front-end modules for more information about FEM in the nRF Connect SDK.

To add support for other front-end modules, add the respective devicetree file entries to the board devicetree file or the devicetree overlay file.

Building and running

This sample can be found under samples/keys/random_hw_unique_key in the nRF Connect SDK folder structure.

To build the sample with Visual Studio Code, follow the steps listed on the How to build an application page in the nRF Connect for VS Code extension documentation. See Building and programming an application for other building and programming scenarios and Testing and debugging an application for general information about testing and debugging in the nRF Connect SDK.

Testing

After programming the sample to your development kit, complete the following steps to test it:

  1. Connect to the kit that runs this sample with a terminal emulator (for example, PuTTY). See How to connect with PuTTY for the required settings.

  2. Reset the kit.

  3. Observe the following output:

    Writing random keys to KMU.
Success!

    If an error occurs, the sample prints a message and raises a kernel panic.

Dependencies

This sample uses the following libraries: