- A
Implement key escrow where the company holds a copy of all users' private keys.
Why wrong: Key escrow defeats E2EE because the company can decrypt any communication.
- B
Implement a transparent encryption proxy on the user's device that logs all keys and sends them to the company.
Why wrong: This proxy would capture keys before encryption, breaking E2EE.
- C
Use client-side encryption where the encryption key is derived from user password and stored with a backup that can be recovered by the company using a master key.
Why wrong: Password-derived keys are weak and master key compromise exposes all data.
- D
Implement a split-key design where the encryption keys are generated and held by the users, but a separate escrow agent splits the key into two parts: one held by the user and one held by the company. Alternatively, use a 'drop box' approach where communications are recorded in an encrypted format and the company can decrypt only after a court order by using a secondary key that is released upon authorization.
This preserves E2EE for routine communications while allowing lawful interception through a separate mechanism.
Quick Answer
The correct answer is a split-key design, which resolves the conflict between end-to-end encryption and lawful interception by dividing the encryption key into two parts—one held by the user and the other by a trusted escrow agent or company. This ensures that neither the cloud provider nor the company can decrypt communications without both key fragments being combined under strict legal authorization, preserving confidentiality for routine use while enabling court-ordered access. On the CISSP exam, this scenario tests your understanding of the trade-off between privacy and legal compliance within the domain of cryptography and security architecture, often appearing as a trap where candidates mistakenly choose a backdoor or weakened encryption. The key insight is that split-key or drop-box designs maintain the integrity of E2EE for everyday operations while satisfying lawful interception mandates through a secondary authorization mechanism. Memory tip: think of a “two-key vault”—one key stays with the user, the other is locked away until a judge’s order unlocks the box.
CISSP Security Architecture and Engineering Practice Question
This CISSP practice question tests your understanding of security architecture and engineering. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 multinational corporation is developing a new cloud-based collaboration platform that handles sensitive intellectual property. The platform must ensure end-to-end encryption (E2EE) so that even the cloud provider cannot access the data. Users communicate via chat and file sharing. The architect proposes using a hybrid encryption scheme where each user has a public/private key pair, and for each message, a random symmetric key is used to encrypt the message, which is then encrypted with the recipient's public key. However, there is a requirement for the company to be able to lawfully intercept communications in case of a court order. This conflicts with E2EE. Which design can satisfy both confidentiality and lawful interception?
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
Implement a split-key design where the encryption keys are generated and held by the users, but a separate escrow agent splits the key into two parts: one held by the user and one held by the company. Alternatively, use a 'drop box' approach where communications are recorded in an encrypted format and the company can decrypt only after a court order by using a secondary key that is released upon authorization.
Option D is correct because it uses a split-key or drop-box design that preserves end-to-end encryption for regular communications while enabling lawful interception under strict authorization. In this scheme, the user holds one part of the key and the company holds another, or communications are recorded encrypted and a secondary key is released only after a court order, ensuring that neither the cloud provider nor the company can decrypt data without proper legal process. This satisfies both the E2EE requirement and the lawful interception mandate without compromising the core security principle of least privilege.
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.
- ✗
Implement key escrow where the company holds a copy of all users' private keys.
Why it's wrong here
Key escrow defeats E2EE because the company can decrypt any communication.
- ✗
Implement a transparent encryption proxy on the user's device that logs all keys and sends them to the company.
Why it's wrong here
This proxy would capture keys before encryption, breaking E2EE.
- ✗
Use client-side encryption where the encryption key is derived from user password and stored with a backup that can be recovered by the company using a master key.
Why it's wrong here
Password-derived keys are weak and master key compromise exposes all data.
- ✓
Implement a split-key design where the encryption keys are generated and held by the users, but a separate escrow agent splits the key into two parts: one held by the user and one held by the company. Alternatively, use a 'drop box' approach where communications are recorded in an encrypted format and the company can decrypt only after a court order by using a secondary key that is released upon authorization.
Why this is correct
This preserves E2EE for routine communications while allowing lawful interception through a separate mechanism.
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 assume key escrow (Option A) is the only way to achieve lawful interception, failing to recognize that escrow breaks E2EE and that split-key or drop-box designs can satisfy both requirements without compromising the confidentiality of all communications.
Detailed technical explanation
How to think about this question
The split-key design often uses threshold cryptography (e.g., Shamir's Secret Sharing) where the decryption key is split into multiple shares; the user holds one share and a trusted escrow agent holds another, and decryption requires both shares to be combined. In the drop-box approach, messages are encrypted with a session key that is itself encrypted under the recipient's public key, and a separate 'lawful access' key pair is used to encrypt a copy of the session key, which is stored and can only be decrypted by the company after a court order releases the corresponding private key. This ensures that even the cloud provider cannot access plaintext data, and the company can only decrypt specific communications when legally authorized.
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
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FAQ
Questions learners often ask
What does this CISSP question test?
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: Implement a split-key design where the encryption keys are generated and held by the users, but a separate escrow agent splits the key into two parts: one held by the user and one held by the company. Alternatively, use a 'drop box' approach where communications are recorded in an encrypted format and the company can decrypt only after a court order by using a secondary key that is released upon authorization. — Option D is correct because it uses a split-key or drop-box design that preserves end-to-end encryption for regular communications while enabling lawful interception under strict authorization. In this scheme, the user holds one part of the key and the company holds another, or communications are recorded encrypted and a secondary key is released only after a court order, ensuring that neither the cloud provider nor the company can decrypt data without proper legal process. This satisfies both the E2EE requirement and the lawful interception mandate without compromising the core security principle of least privilege.
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: Jun 24, 2026
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