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doc: add kmu provisioning info #21030

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Mar 20, 2025
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doc: add kmu provisioning info #21030

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1 change: 1 addition & 0 deletions doc/nrf/app_dev/device_guides/nrf54l/fota_update.rst
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Expand Up @@ -193,6 +193,7 @@ Provisioning of keys for Hardware KMU
*************************************

In case of FOTA implementations using the MCUboot bootloader, which includes hardware cryptography and KMU, you must complete key provisioning before booting any application.
Otherwise, the bootloader :ref:`may not boot the firmware setup and might take unwanted actions<ug_nrf54l_developing_basics_kmu_provisioning_keys>`.
Refer to :ref:`ug_nrf54l_developing_provision_kmu` for detailed description.

.. _ug_nrf54l_developing_ble_fota_mcuboot_direct_xip_mode:
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10 changes: 10 additions & 0 deletions doc/nrf/app_dev/device_guides/nrf54l/kmu_basics.rst
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Expand Up @@ -35,12 +35,22 @@ Locked keys
Once provisioned, locked keys are permanently available for use and cannot be deleted without erasing the device.
For these keys, the revocation policy (RPOLICY) must be marked as ``locked``.

.. _ug_nrf54l_developing_basics_kmu_provisioning_keys:

Provisioning keys for the bootloader
************************************

The bootloader can use multiple key generations for image verification (up to three for nRF54L SoCs).
To safeguard against unauthorized provisioning by attackers, you must :ref:`provision all key generations onto the device<ug_nrf54l_developing_provision_kmu>`.

Make sure to provision the setup’s relevant key sets before any run with bootloaders, including the first boot.
Failure to do so can lead to unwanted actions by the bootloader on your firmware setup.
You may experience the following issues:

* The nRF Secure Immutable Bootloader (NSIB) will mark the image as permanently invalid without a key available for verification.
* In direct-xip mode, MCUboot will delete the image if no appropriate key is provisioned.
* The firmware will simply not boot, indicating a lack of proper key provisioning.

By default, MCUboot uses a single key.
You can configure the number of key generations that MCUboot uses for application verification with the ``CONFIG_BOOT_SIGNATURE_KMU_SLOTS`` MCUboot's Kconfig option.

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2 changes: 2 additions & 0 deletions doc/nrf/app_dev/device_guides/nrf54l/kmu_provision.rst
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Expand Up @@ -22,6 +22,8 @@ Once completed, install the required additional commands for nRF Util:

nrfutil install device

Additionally, before provisioning, make sure you familiarized yourself with the :ref:`ug_nrf54l_developing_basics_kmu_provisioning_keys` section.

.. _ug_nrf54l_developing_provision_kmu_generate:

Key generation
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