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Security Fundamentals & Crypto · Intermediate

Secure Boot

UEFI feature that allows only cryptographically signed bootloaders and OS components to run at startup.

Definition

Secure Boot verifies digital signatures of firmware drivers, bootloaders, and kernels against keys stored in UEFI databases (PK, KEK, db, dbx). It blocks bootkits and unsigned boot code. Microsoft is replacing its 2011 Secure Boot certificates, which expire in 2026, with 2023 certificates.

Example

A rootkit that modifies the Windows bootloader fails to load because its signature does not match the db.

Exam tip

Secure Boot prevents unsigned boot code; Measured Boot records what loaded for attestation.

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