Signed boot is a startup security check that verifies a firmware image’s cryptographic signature before the device executes it. The bootloader or secure boot ROM compares the firmware against a trusted public key, and only code with a valid signature is allowed to run. This helps ensure that the software on the device has not been altered by an attacker or corrupted during update.
In cyber security, signed boot matters because firmware is a high-value target: if an attacker can replace it, they can gain persistent control, hide malware, or disable security features. It is common in embedded systems, microcontrollers, phones, and industrial devices. Defenders use signed boot with secure update pipelines, key management, and hardware-backed trust to reduce tampering risk. Attackers, by contrast, may try to bypass it through physical access, debug interfaces, or stolen signing keys. Signed boot does not stop all compromise, but it raises the cost of running untrusted code at the earliest stage of startup.