Over the air (OTA) updates have become an essential component for maintaining device functionality, deploying new features and addressing security vulnerabilities. OTA updates allow manufacturers to manage large-scale IoT networks by updating software remotely which eliminates the requirement for physical access for each device.
Growing importance of OTA updates
IoT devices are increasingly embedded in critical infrastructure, from industrial systems to smart homes and medical equipment. As these devices perform crucial tasks, keeping their software up-to-date is essential. OTA updates enable remote firmware or software modifications, which can be deployed to thousands or even millions of devices without manual intervention.
However, this convenience brings its own set of challenges. The sheer volume of data involved in OTA updates, combined with the growing number of connected devices, introduces vulnerabilities that malicious actors could exploit. Hackers can attempt to intercept updates, inject malware, or disrupt the update process, leaving networks exposed to cyberattacks.
Best practices for securing OTA updates
Securing OTA updates requires a multi-layered approach, with a strong emphasis on encryption, authentication, and device integrity verification.
1. Encryption
Data encryption is the cornerstone of securing OTA updates. The update package, which contains the new firmware or software, must be encrypted to prevent unauthorised access during transmission. Encryption ensures that even if an attacker intercepts the update, they cannot read or modify its contents.
A widely used encryption method is Advanced Encryption Standard (AES), which is favoured for its balance between security and computational efficiency. AES-256, for example, offers a high level of security and is considered practically unbreakable under current technological capabilities. In OTA updates, AES can be used to encrypt both the payload (the firmware or software being delivered) and the communication channel itself, adding an extra layer of protection.
2. Authentication protocols
Authentication ensures that only authorised entities can send OTA updates to a device. Without proper authentication, malicious actors could impersonate legitimate update sources, sending corrupted updates or malware-laden files.
Public Key Infrastructure (PKI) is a widely used method to authenticate OTA updates. In PKI, the manufacturer (or update server) uses a private key to sign the update package. The IoT device, in turn, uses a corresponding public key to verify the signature, ensuring that the update comes from a trusted source. If the signature does not match, the device can reject the update, preventing any unauthorised software from being installed.
Additionally, Transport Layer Security (TLS) protocols can be employed to secure communication between the update server and IoT devices, providing encryption, authentication, and data integrity checks.
3. Secure bootloaders
A secure bootloader is a vital component in ensuring the integrity of an IoT device after an OTA update is applied. The bootloader is responsible for verifying the authenticity and integrity of the software during the boot-up process. If the software has been tampered with, the bootloader will detect the modification and halt the boot process, preventing potentially harmful code from executing.
Many secure bootloaders implement cryptographic techniques, such as hash functions or digital signatures, to verify that the software has not been altered. Secure bootloaders are often used in conjunction with hardware-based security features like Trusted Platform Modules (TPMs), which further enhance the device’s ability to protect itself from unauthorised modifications.
Challenges of scaling OTA updates
As IoT networks grow, the scalability of OTA updates becomes a major concern. Deploying updates to tens of thousands or millions of devices simultaneously introduces technical challenges that must be addressed to ensure smooth and secure updates.
1. Bandwidth constraints
One of the most significant challenges in scaling OTA updates is managing bandwidth. IoT devices are often deployed in bandwidth-constrained environments, such as remote locations or dense urban areas where network capacity may be limited. Transmitting large update files to thousands of devices simultaneously can strain the network, leading to slow updates, dropped connections, or failed installations.
To mitigate these issues, manufacturers can employ techniques such as delta updates. A delta update only contains the difference between the current firmware and the new version, reducing the size of the data package. By sending smaller updates, the demand on network bandwidth is lessened, allowing more devices to receive updates concurrently without overwhelming the network.
2. Synchronisation Issues
Synchronising updates across a massive network of IoT devices can be another challenge. In large-scale IoT deployments, devices may be located across multiple time zones, connected to different networks, or powered by different energy sources. Scheduling updates to occur at the same time can lead to conflicts, particularly if some devices are temporarily offline or experiencing power outages.
One solution to this issue is staggered update deployment. Rather than pushing updates to all devices simultaneously, manufacturers can roll out updates in waves, ensuring that the network is not overloaded and allowing time for troubleshooting if issues arise. Devices can also be configured to check for updates at random intervals, distributing the load more evenly across the network.
3. Device diversity and compatibility
Large IoT networks will often consist of devices with varying hardware capabilities, operating systems, and communication protocols. Ensuring that an OTA update is compatible with all devices in the network is a complex task, as a one-size-fits-all update may not work for every device.
Manufacturers can address this by segmenting devices into groups based on their capabilities and developing custom update packages for each group. This approach allows updates to be tailored to specific device types, ensuring compatibility and reducing the likelihood of update failures.
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