As the Internet of Things (IoT) continues to proliferate, the security of edge devices—those operating on the periphery of networks—becomes increasingly critical. These devices, often situated in uncontrolled environments, are vulnerable to various forms of attacks, ranging from remote unauthorized access to physical tampering. To fortify the defense of these devices, solutions such as Secure Element Chips, Tamper Detection hardware, as well as fully assembled and encapsulated general-purpose secured computing platforms are gaining traction.

Core Security Strategies: Trusted Platform Modules and Secure Elements

At the core of edge device security strategies lies the integration of Trusted Platform Modules (TPM) or Secure Elements (SE). These hardware-based solutions serve as a cornerstone in establishing trust at the device level. By leveraging hardware cryptographic accelerators, a true random number generator, and secure key storage, they ensure that sensitive key material remains protected from unauthorized access. Their adoption not only enhances security but also simplifies the deployment and management of IoT devices, even for organizations lacking extensive security expertise.

Design and System Development Considerations:

For engineers looking to incorporate Secure Elements into their projects, careful consideration should be given to the selection of SEs that align with the security needs of the specific application. Integration involves using microcontrollers or processors that support secure boot and cryptographic operations. The hardware design should include dedicated I2C or SPI communication lines to the SE, ensuring data integrity and security during transmission. Additionally, software development should leverage available APIs provided by SE manufacturers, such as Microchip’s CryptoAuthLib, which simplifies the process of implementing secure key storage and encryption.

Secure Elements in Cryptographic Applications

Secure elements provide functionalities used in a wide range of cryptographic applications, including blockchain-related ones. Examples include provisioning unique identifiers for device authentication (generated either during manufacturing or dynamically at runtime), generating random values from internal noise sources (making sure adequate entropy is maintained when utilized), and implementing various cipher suites that meet industry standards like those set by NIST (National Institute of Standards and Technology at the U.S. Department of Commerce). Furthermore, when coupled with their accompanying toolsets, secure elements such as Microchip’s ATECC608B and its Trust Platform, enable effortless integration with cloud-based platforms like AWS IoT.

Integration Tips:

When implementing secure element chips in your project, consider the following:

• Provisioning: Decide if your device will use static or dynamic keys and configure your SE accordingly.
• Random Number Generation: Ensure that your application leverages the SE’s true random number generator to avoid predictable keys.
• Cipher Suite Selection: Match the SE’s available cipher suites with the security requirements of your target application and compliance needs.

Motion Sensor Tamper Detection: An Additional Layer of Defense

In addition to robust cryptographic measures, motion sensors (e.g., accelerometers) can be used for tamper detection to add another layer of defense against physical attacks. These sensors, strategically placed within the device enclosure, monitor changes in orientation or movement. Any unauthorized attempt to open or tamper with the device triggers an alert, allowing for immediate response and mitigation. This ensures the integrity of sensitive data by locking it or even destroying it if a possible breach is detected.

Engineering Focus:

To effectively incorporate motion sensor-based tamper detection:

• Sensor Placement: Determine optimal sensor placement within the enclosure to detect unauthorized movement without triggering false positives.
• Sensitivity Calibration: Calibrate the sensor’s sensitivity based on the operational environment to differentiate between normal usage and potential tampering.
• Interrupt Handling: Implement software routines to handle interrupts generated by the motion sensor, triggering security protocols such as data encryption or system shutdown.

Power Supply Monitoring: Ensuring Continuous Operation

Further methodologies include monitoring the main power supply, as well as possible auxiliary batteries, to ensure continuous availability of power to critical components. By closely monitoring power sources, anomalies such as sudden power surges, fluctuations, or unexpected power outages can be detected promptly, alerting cybersecurity teams to potential threats or attempted breaches. Additionally, monitoring auxiliary batteries ensures that backup power systems are functioning correctly, providing resilience against power-related cyberattacks or disruptions.

Design Considerations:

• Redundancy: Design redundant power systems with failover mechanisms to maintain operation during a primary power failure.
• Data Logging: Implement data logging for power metrics to analyze patterns that might indicate tampering attempts or power instability.

Power Glitch Attacks:

In the context of power supply monitoring, it’s essential to consider power glitch attacks, where attackers deliberately induce brief power interruptions or voltage spikes to destabilize or bypass security mechanisms. These attacks can lead to unexpected behavior in edge devices, such as skipping security checks during reboot or causing malfunctions in cryptographic operations. To mitigate such risks, design engineers should ensure that devices have appropriate brown-out detection and that the firmware is capable of handling unexpected power glitches gracefully. Incorporating robust power supply circuits with proper filtering and surge protection can also help in defending against these types of attacks.

The Importance of Layered Security

Protection against threats requires a layered security approach, which combines multiple considerations and mechanisms to create a robust defense. This includes not only hardware-based solutions like Secure Elements and tamper detection but also software strategies such as secure boot, encryption, and regular firmware updates. By integrating these diverse layers of security, engineers can create a resilient system where each layer reinforces the other, minimizing the risk of successful attacks and ensuring comprehensive protection for edge devices.

Sfera Labs’ Strato Pi Max: A Comprehensive Security Solution

An example of a solution incorporating these security measures is Sfera Labs’ Strato Pi Max, which combines a Raspberry Pi Compute Module and an RP2040 microcontroller with a modular and expandable set of security, safety, and fault-resilience features to address a variety of scenarios. Strato Pi Max also offers the option of using Zymbit’s Secure Compute Module (SCM) as the processing core to further enhance security capabilities. Strato Pi Max’s expansions include an uninterruptible power supply (UPS) with auxiliary power output that can be used to power external devices. The platform also supports several redundancy storage options, including embedded eMMC, SSDs, and dual SD cards, allowing for data recovery and system restoration in case of storage failures.

Practical Implementation:

When working with platforms like the Strato Pi Max:

• Modular Integration: Leverage the modularity to add or swap security components based on your application’s evolving needs.
• Customization: Customize the I/O interfaces to connect additional sensors or actuators required by your specific use case.
• Powering External Devices: Utilize the auxiliary power supply output to keep critical external devices, such as modems, powered during outages, ensuring continuous operation and communication.
• Redundant Storage: Take advantage of the multiple storage options to ensure system/data redundancy and facilitate recovery from storage failures.

As the IoT landscape continues to evolve, the importance of robust security measures cannot be overstated. The above-mentioned solutions represent critical components in safeguarding edge devices against a myriad of threats. By leveraging these technologies, companies like Sfera Labs are at the forefront of innovation, delivering secure and resilient solutions that meet the demands of today’s interconnected world. As threats evolve, staying ahead of the curve requires a proactive stance towards security, embracing cutting-edge technologies to fortify the defenses of edge devices and ensure a secure foundation for the IoT ecosystem.

By Giampiero Baggiani, Co-Founder and Head of Software Development at Sfera Labs.