The correct answer is to use a TPM to measure boot components and compare to stored hashes, as this provides the highest assurance of firmware integrity for resource-constrained IoT devices. A Trusted Platform Module offers hardware-rooted trust by recording measurements of each boot stage—such as the BIOS, bootloader, and OS kernel—into Platform Configuration Registers (PCRs), then comparing them against known-good hashes stored securely within the TPM. This process, known as IoT secure boot with TPM for firmware integrity, ensures that any unauthorized modification is detected before execution, relying on immutable hardware rather than fallible software checks. On the CISSP exam, this concept tests your understanding of the Secure Boot and Trusted Platform Module domains within the Security Architecture and Engineering domain; a common trap is to select software-based solutions like digital signatures alone, which lack hardware anchoring. Remember the mnemonic “TPM PCRs Protect” to recall that the TPM’s PCRs provide the protective measurement chain for boot integrity.
CISSP Security Architecture and Engineering Practice Question
This CISSP practice question tests your understanding of security architecture and engineering. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company is designing secure boot for IoT devices to ensure only trusted firmware runs. The devices have limited resources. Which mechanism provides the highest assurance of boot integrity?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a TPM to measure boot components and compare to stored hashes.
Option C is correct because a Trusted Platform Module (TPM) provides hardware-rooted trust by measuring each boot component (e.g., BIOS, bootloader, OS kernel) and storing the measurements in Platform Configuration Registers (PCRs). These measurements are compared against known-good hashes stored in the TPM, ensuring that any tampering with firmware is detected before execution. This offers the highest assurance for resource-constrained IoT devices as it relies on immutable hardware rather than software-based checks.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Use a software-based integrity check that runs after boot.
Why it's wrong here
Software checks can be subverted if the boot process is already compromised.
✗
Set a BIOS password to prevent unauthorized changes.
Why it's wrong here
A BIOS password does not verify the integrity of firmware.
✓
Use a TPM to measure boot components and compare to stored hashes.
Why this is correct
TPM provides hardware-based integrity measurement and storage.
Related concept
Read the scenario before looking for a memorised answer.
✗
Implement full disk encryption (FDE).
Why it's wrong here
FDE protects data at rest but does not ensure that the boot firmware is trusted.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse integrity verification (ensuring code hasn't been tampered with) with confidentiality protections (like encryption) or access controls (like passwords), leading them to pick full disk encryption or BIOS passwords instead of the hardware-based attestation provided by a TPM.
Detailed technical explanation
How to think about this question
The TPM uses a process called 'measured boot' where each component (e.g., BIOS, bootloader) extends its hash into a PCR before executing the next component, creating a cryptographic chain of trust. If any component is altered, the final PCR value will differ from the expected value stored in the TPM's non-volatile memory, causing the boot to fail or trigger a remediation action. In real-world IoT scenarios, such as medical devices or industrial controllers, this prevents rootkits like BadUSB or bootkits from persisting across reboots.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CISSP question in full detail.
Security Architecture and Engineering — This question tests Security Architecture and Engineering — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use a TPM to measure boot components and compare to stored hashes. — Option C is correct because a Trusted Platform Module (TPM) provides hardware-rooted trust by measuring each boot component (e.g., BIOS, bootloader, OS kernel) and storing the measurements in Platform Configuration Registers (PCRs). These measurements are compared against known-good hashes stored in the TPM, ensuring that any tampering with firmware is detected before execution. This offers the highest assurance for resource-constrained IoT devices as it relies on immutable hardware rather than software-based checks.
What should I do if I get this CISSP question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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