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tutorial updated and tested
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mcmchris committed Sep 11, 2025
commit fc1fb442707527e7f1ee091e81ae34deb87d632e
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Original file line number Diff line number Diff line change
Expand Up @@ -4,12 +4,11 @@ description: 'Learn how to use secure boot on the Arduino Portenta H7.'
difficulty: beginner
tags:
- Secure Boot
author: 'Umberto Baldi'
author: 'Umberto Baldi & Christopher Méndez'
hardware:
- hardware/04.pro/boards/portenta-h7

software:
- ide-v1
- ide-v2
- cli
---
Expand All @@ -35,6 +34,27 @@ In order to enable the secure boot, you must **update** the bootloader on your P

Once the bootloader has been updated, it is possible to use [secure boot](https://www.keyfactor.com/blog/what-is-secure-boot-its-where-iot-security-starts/) to have an additional layer of security.

### Format the QSPI Flash

First, before enabling the secure boot feature on your Portenta H7, you might need to format the QSPI flash memory.

For this, navigate to **File > Examples > STM32H747_System > QSPIFormat** and follow the steps below:

![QSPIFormat example code](assets/qspi-format.png)

- Upload the **QSPIFormat** example to your Portenta H7.
- Open the Arduino IDE Serial Monitor.
- Follow the steps shown in the Serial Monitor.

You will be asked for:

- Permission to proceed and **erase** the QSPI flash. Type `Y` in the Serial Monitor and press enter.
- Once done, you will be asked to **restore** the WiFi firmware. Type `Y` in the Serial Monitor and press enter.
- Select between **LitteFS** or **FatFS** to format user partition. Type `Y` for LittleFS or `No` for FatFS.
- Wait for the process to be done. It should say something like "It is now secure to reboot or disconnect the board".

Now you are ready to jump to the following step to enable the secure boot.

### Use Default Security Keys

Upload the `enableSecurity` example sketch that can be found under **File > Examples > MCUboot** in the IDE upper menu.
Expand All @@ -60,7 +80,8 @@ From that point on, you must configure your future sketches **Security setting**

***Not configuring this setting will cause the bootloader not to run the compiled sketch because it is not trusted.***

### 1. Generate Custom Security Keys
### Generate Custom Security Keys

The default keys provided with the mbed platform are obviously only intended for development purposes. In a production environment it is strongly recommended to generate a new key pair (public and private key).
This can be done with **imgtool**. You can download and install it directly from the [release section](https://github.com/arduino/imgtool-packing/releases/latest).

Expand All @@ -72,17 +93,17 @@ The tool can be found in:
- `~/.arduino15/packages/arduino/tools/imgtool` on Linux.
- `~/Library/Arduino15/packages/arduino/tools/imgtool` on macOS.

To generate the new keys you can use this command line:
To **generate** the new keys you can use this command line:

```bash
imgtool keygen --key my-sign-keyfile.pem -t ecdsa-p256
imgtool keygen --key my-encrypt-keyfile.pem -t ecdsa-p256
```
This command line will generate two private PEM encoded security keys and save them in the current directory with `my-sign-keyfile.pem` and `my-encrypt-keyfile.pem` names. The algorithm used to generate the keys is ECDSA 256bit.

Remember to **save the keys and keep them in a secure location** and not to lose them.
***Remember to __save the keys and keep them in a secure location__ and not to lose them.***

### 2. Upload the Custom Keys to the Board
### Upload the Custom Keys to the Board
Once the keys have been generated, they have to be uploaded to the Portenta H7. This procedure has to be done only once, because it is persistent. To extract the public\private key and encode it in to a "C" byte array inside a `.h` header file you can use:

```bash
Expand All @@ -94,16 +115,27 @@ Now you have to replace the keys inside the `enableSecurity` sketch found under

To do so, just save the sketch to another location and replace the `ecsda-p256-encrypt-priv-key.h` and `ecsda-p256-signing-pub-key.h` files with the newly generated ones and then upload the sketch again.

***NOTE: In case the keys are compromised, this process can be performed again with a new set of keys, but any firmware signed with the previous pair will no longer work.***
***__NOTE:__ In case the keys are compromised, this process can be performed again with a new set of keys, but any firmware signed with the previous pair will no longer work.***

### 3. Use the Custom Keys when Compiling
### Use the Custom Keys when Compiling
Since the default keys have been changed in favour of custom generated ones, the new ones have to be used when compiling and uploading a sketch, because the compiled sketch is signed and encrypted using such keys.

To override the security keys used during the compilation, you have to use the Arduino CLI and specify the keys with:
To override the security keys used during the compilation, we recommend using the **Arduino CLI** and specify the keys with:

```bash
arduino-cli compile -b arduino:mbed_portenta:envie_m7 --board-options security=sien --keys-keychain <path-to-your-keys> --sign-key ecdsa-p256-signing-priv-key.pem --encrypt-key ecdsa-p256-encrypt-pub-key.pem <directory-of-sketch-to-compile>
```

You can also navigate to your `mbed_portenta` core found in:

- `%LOCALAPPDATA%\Arduino15\packages\arduino\hardware\mbed_portenta\x.x.x\boards.txt` (this may vary depending on the operating system).
- Then, change the default location your IDE search for the security keys by updating these lines inside the `boards.txt` file:

```bash
envie_m7.menu.security.sien.build.keys.keychain={runtime.platform.path}/libraries/MCUboot/default_keys
envie_m7.menu.security.sien.build.keys.sign_key=ecdsa-p256-signing-priv-key.pem
envie_m7.menu.security.sien.build.keys.encrypt_key=ecdsa-p256-encrypt-pub-key.pem
```

## Learn More
If you want to implement secure boot for your platform, have a look at [this article](https://arduino.github.io/arduino-cli/latest/guides/secure-boot/).
If you want to implement secure boot for your platform, take a look at [this article](https://arduino.github.io/arduino-cli/latest/guides/secure-boot/).