How do you implement and update firmware over the air (FOTA) securely?

Just one compromised firmware update delivered to a control unit in a car or airplane can lead to a tragedy. Imagine if this firmware affected the brake control module... Or if the firmware managing a smart home's heating system was compromised. Picture thermostats setting incorrect temperatures or security cameras failing to record, causing inconvenience and potential safety risks. This is truly important.

Absolutely, FOTA security is non-negotiable. During my experience with embedded systems, I’ve seen firsthand how a lack of robust security can jeopardize both functionality and trust. Implementing end-to-end encryption for firmware delivery and validating updates using cryptographic signatures has been a game-changer for maintaining device integrity. A compromised update isn’t just a technical problem—it can lead to loss of customer confidence, which is far harder to rebuild than the firmware itself.

Security in FOTA is paramount because it protects devices from malicious attacks that could compromise their functionality or endanger users. For instance, an attacker gaining unauthorized access to firmware could lead to device bricking, data theft, or even physical harm in critical applications like healthcare or automotive systems. FOTA also builds user trust by ensuring updates enhance device performance without introducing vulnerabilities.

These are a few simple checks that can implemented to secure an OTA update - 1. Checksums 2. Implementing a custom packet design - check if headers match, if length of message is correct, if expected data is present at a certain index in the received packet etc. 3. Have ID numbers that represent the firmware or hardware and checking if the received packet contains an exact match. 4. Limiting the number of system states in which FOTA can occur.

I completely agree—secure boot and hardware security modules (HSM) are lifesavers in modern embedded systems. In one project, we integrated dual-layer secure storage to handle sensitive data, ensuring encryption keys were isolated. This approach dramatically improved security and helped the team meet stringent regulatory requirements.

The authentication and integrity checks should be strictly implemented along with the choice for right cryptographic algorithms to make FOTA package secure.

Hardware forms the foundation of FOTA security. Features like secure boot validate firmware authenticity at startup, ensuring only signed and trusted software runs on the device. Trusted Platform Modules (TPMs) securely store cryptographic keys, while secure enclaves isolate sensitive operations from the rest of the system. Additionally, write-protected memory regions prevent unauthorized modifications to critical firmware sections, and a hardware root of trust provides a baseline for verifying firmware integrity.

Choosing the best FOTA update method depends on device requirements and operational constraints. For always-connected devices, push updates ensure timely delivery, whereas pull updates are ideal for intermittently connected systems. Using secure protocols like HTTPS or MQTT with TLS safeguards communication, and delta updates optimize bandwidth by transmitting only firmware changes. Fallback mechanisms are also crucial, allowing devices to revert to a previous firmware version if an update fails, reducing the risk of device downtime.

FOTA updates complexity increases with the decrease in memory. The less the available memory the more complex FOTA solution will be. It will require various factors to consider including differential updates, rollback support, and power-loss recovery.

Absolutely agree, and I’d add that dual-bank updates are a lifesaver for critical systems. While working on a real-time drone application, we relied on dual-bank updates to allow seamless rollbacks. This ensured that even in case of update failures, operations could continue with minimal disruption.

Totally agrees with the testing approach mentioned here. FOTA patching can be tested on host with simulated environments. But system testing with actual hardware is always crucial in debugging and production mode.

Absolutely agree—thorough testing ensures reliability. During my work with drone firmware updates, integration testing was key to avoiding conflicts between modules. Using debuggers and analyzers helped us uncover subtle issues, while staging environments let us validate updates under realistic conditions.

Testing is integral to successful FOTA deployment. Before releasing updates, simulations in virtual environments can identify potential issues. Staging deployments—where updates are rolled out incrementally—mitigate risks by limiting exposure to a small subset of devices. Automated testing frameworks can validate device functionality post-update, while checksum validation ensures firmware integrity throughout the process. For debugging, detailed logging mechanisms provide critical insights into update failures.

Creating your own FOTA server is one way of doing it. You have to manage the DB with list of devices, along with the FW version and other important info. The server and DB can all be hosted on Amazon or any other provider.

A centralized management platform simplifies FOTA processes by tracking device statuses and firmware versions. Real-time monitoring enables quick detection and resolution of update issues, while analytics provide valuable insights into performance metrics like update success rates. Security is enhanced through device authentication with unique keys or certificates. Finally, clear user communication fosters transparency, informing users about update schedules and benefits.