Secure Boot checks the signature on the bootloader before it runs. Trusted Boot carries that check forward to the kernel and boot drivers. Measured Boot does something different: it records hashes of what loaded so a remote server can judge health. The first two block, the third reports.
Secure Boot: the first gate
On a PC with UEFI firmware, Secure Boot makes the firmware examine the bootloader's digital signature before starting it. Microsoft's documentation says the bootloader runs only if it was signed with a trusted certificate or the user approved its signature by hand. Without Secure Boot, the machine runs whatever bootloader it finds on disk and has no way to tell a trusted one from a rootkit.
Microsoft also notes that software cannot change the Secure Boot settings. A person has to do it in the firmware menu. That detail matters for threat models, because it separates a remote attacker from one with hands on the machine.
Trusted Boot: the next link
Trusted Boot picks up where Secure Boot stops. In Microsoft's description, the bootloader verifies the signature on the Windows kernel, and the kernel verifies the rest of the startup path, including boot drivers. If a file was modified, the component is refused, and Windows can often repair it.
The pattern is a chain. Each stage checks the next one before handing over control. The same idea shows up in embedded devices and phones, with a different first link.
Measured Boot: evidence, not enforcement
Measured Boot does not stop anything from loading. The firmware stores hashes of the firmware, bootloader and boot drivers in the TPM. Later, a remote attestation server can ask the TPM to sign that log and decide whether the machine looks healthy, for example by sending it to a quarantine network.
Microsoft points out you need non-Microsoft tools for the attestation client and server. So Measured Boot gives you the raw material, and the policy is yours to build.
Which one do you need?
If your question is "can malware replace my bootloader," the answer is Secure Boot. If it is "can something tamper with the kernel or early drivers," look at Trusted Boot. If it is "how do I know a remote machine started clean, given that a rootkit can lie," you want measurement plus attestation.
For a device maker the lesson is the same in a different shape. Verify each stage, and decide in advance what happens when a check fails. A device that quietly boots unsigned code has no secure boot, whatever the data sheet says.
Quick check
Does Secure Boot stop all firmware attacks?
No. It checks signed boot components. It does not prove the firmware itself is free of bugs, and Microsoft describes separate features for the later stages.
Is Measured Boot the same as Secure Boot?
No. Secure Boot blocks unsigned bootloaders. Measured Boot records hashes in the TPM so a server can assess the result afterwards.
Where Safeguard fits
Safeguard does not replace a bootloader or a hardware root of trust. It covers the software side around them: SBOM and dependency scanning for the components that end up in your builds, policies and gates that block a risky release, and compliance evidence. You can try a free scan at gold.safeguard.sh/scan.
Sources
Last reviewed: 19 October 2026.
