- A
S/MIME
Why wrong: S/MIME uses a hierarchical PKI with certificate authorities.
- B
TLS
Why wrong: TLS secures communication channels, not email messages.
- C
SSH
Why wrong: SSH secures remote login and file transfer, not email.
- D
PGP/GPG
PGP/GPG employs a decentralized web of trust for key verification.
Question 19 of 1,000
CISSP Communication and Network Security Practice Question
This CISSP practice question tests your understanding of communication and network security. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
An organization wants to secure email communications by providing encryption and digital signatures. They require a solution that uses a web of trust model rather than a hierarchical PKI. Which protocol should they implement?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
PGP/GPG
PGP/GPG implements a web of trust model where users sign each other's keys to establish trust, rather than relying on a centralized Certificate Authority (CA). It provides both encryption and digital signatures for email, making it the correct choice for an organization that explicitly wants to avoid hierarchical PKI.
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.
- ✗
S/MIME
Why it's wrong here
S/MIME uses a hierarchical PKI with certificate authorities.
- ✗
TLS
Why it's wrong here
TLS secures communication channels, not email messages.
- ✗
SSH
Why it's wrong here
SSH secures remote login and file transfer, not email.
- ✓
PGP/GPG
Why this is correct
PGP/GPG employs a decentralized web of trust for key verification.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse S/MIME and PGP because both provide email security, but the key differentiator is the trust model—S/MIME uses a hierarchical PKI, while PGP uses a web of trust—and the question explicitly requires the latter.
Detailed technical explanation
How to think about this question
PGP uses a decentralized trust model where each user maintains a keyring of trusted public keys, and trust is established through signatures (e.g., 'I trust Alice because Bob signed her key'). The protocol employs a hybrid cryptosystem: a session key encrypted with the recipient's RSA or ECC public key, while the message is encrypted with a symmetric cipher like AES. Digital signatures are created by hashing the message (e.g., SHA-256) and signing the hash with the sender's private key.
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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this CISSP question test?
Communication and Network Security — This question tests Communication and Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: PGP/GPG — PGP/GPG implements a web of trust model where users sign each other's keys to establish trust, rather than relying on a centralized Certificate Authority (CA). It provides both encryption and digital signatures for email, making it the correct choice for an organization that explicitly wants to avoid hierarchical PKI.
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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Last reviewed: Jul 4, 2026
This CISSP practice question is part of Courseiva's free ISC2 certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CISSP exam.
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