The CySA+ exam outline calls out “trusted firmware updates,” but trusted firmware itself is more commonly described as part of trusted execution environments (TEEs). Trusted firmware is signed by a chip vendor or other trusted party, and then used to access keys to help control access to hardware. TEEs like those used by ARM processors leverage these technologies to protect the hardware by preventing unsigned code from using privileged features."
Trusted firmware updates provide organizations with secure code signing, distribution, installation, and attestation for embedded devices. Embedded devices are devices that have a dedicated function and are part of a larger system or network, such as routers, cameras, sensors, etc. Embedded devices often run on firmware, which is a type of software that controls the device’s hardware and functionality. Firmware updates are essential for improving the performance, security, and reliability of embedded devices. However, firmware updates also pose risks of introducing vulnerabilities or malware into the devices if they are not properly secured. Trusted firmware updates are firmware updates that use cryptographic techniques to ensure the integrity, authenticity, and confidentiality of the firmware code and data. Trusted firmware updates typically involve four steps1:
Code signing: The firmware code is digitally signed by the firmware developer or provider using a private key. The digital signature proves that the firmware code is from a trusted source and has not been tampered with.
Distribution: The signed firmware code is securely transmitted to the embedded device or a trusted intermediary (such as a cloud service or a gateway) using encryption or other methods. The transmission ensures that the firmware code is not intercepted or modified by unauthorized parties.
Installation: The embedded device verifies the digital signature of the firmware code using a public key that is stored in a secure location (such as a trusted platform module or TPM). The verification ensures that the firmware code is from a trusted source and has not been tampered with. The embedded device then installs the firmware code and reboots to apply the update.
Attestation: The embedded device reports its firmware status and configuration to a trusted verifier (such as a cloud service or a gateway) using a cryptographic proof. The proof ensures that the embedded device has installed the correct firmware update and has not been compromised.
Trusted firmware updates provide organizations with several benefits for hardware assurance, such as2:
Preventing unauthorized or malicious firmware updates that could compromise the security or functionality of embedded devices
Detecting and mitigating firmware attacks or incidents that could affect the availability or performance of embedded devices
Complying with regulatory or industry standards or best practices for firmware security
Enhancing customer trust and satisfaction with embedded devices
Trusted firmware updates do not provide organizations with development, compilation, remote access, or customization for embedded devices (A), as these are software engineering tasks that are not directly related to firmware security. Trusted firmware updates do not provide organizations with security specifications, open-source libraries, or custom tools for embedded devices (B), as these are software resources that are not directly related to firmware security. Trusted firmware updates do not provide organizations with remote code execution, distribution, maintenance, or extended warranties for embedded devices ©, as these are software features or services that are not directly related to firmware security.
References: 1: https://www.techopedia.com/definition/24771/technical-controls 2: https://www.techopedia.com/definition/25888/security-development-lifecycle-sdl
