hardMultiple ChoiceObjective-mapped
CISSP Practice Question: A multinational corporation is developing a new…
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?
⚠ Common exam trap
Test-takers frequently 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.
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.
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.
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
Implementing key escrow where the company holds a copy of users' private keys directly undermines End-to-End Encryption (E2EE). E2EE's security relies on only the intended recipient possessing the private key, ensuring confidentiality and integrity of communications. If the company possesses these keys, it can decrypt any communication at will, completely negating the privacy and security guarantees of E2EE for all users.
- ✗
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
A transparent encryption proxy on the user's device that logs and sends all keys to the company fundamentally breaks End-to-End Encryption. Such a proxy operates as a man-in-the-middle, capturing the plaintext encryption keys *before* they are used to encrypt data on the user's device. Sending these pre-encryption keys to the company allows them to decrypt all communications, rendering E2EE ineffective by compromising the key at its source.
- ✗
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
Using client-side encryption with keys derived solely from user passwords introduces significant vulnerabilities, as such keys are often weaker and more susceptible to brute-force or dictionary attacks than cryptographically random keys. Furthermore, storing a backup key recoverable by a company's master key creates a single point of failure. Compromise of this master key would grant unauthorized access to *all* user data, completely undermining the confidentiality and integrity E2EE aims to provide.
- ✓
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
A split-key design maintains End-to-End Encryption (E2EE) by ensuring users retain a critical part of their encryption key, preventing unilateral decryption by the company. Lawful access requires cooperation to reconstruct the key from parts held by the user and an authorized escrow agent. Alternatively, a 'drop box' approach stores encrypted communications, only allowing company decryption via a secondary key released exclusively upon a valid court order, thus preserving E2EE for routine use while enabling legally mandated access.
Visual reference
Quick reference
Symmetric Encryption Algorithm Comparison
| Algorithm | Key Size | Block Size | Status | Notes |
|---|---|---|---|---|
| AES-128 | 128-bit | 128-bit | Current standard | NIST approved; WPA3, TLS |
| AES-256 | 256-bit | 128-bit | Current standard | Preferred for sensitive / govt data |
| 3DES | 112-bit effective | 64-bit | Deprecated (2023) | Replaced by AES |
| DES | 56-bit | 64-bit | Broken | Cracked in < 24 h; never deploy |
| ChaCha20 | 256-bit | Stream cipher | Current | TLS 1.3, WireGuard |
Go deeper
Related to this question
Learn chapter
Security Governance and Principles
Key term
Security
Security in IT is the practice of protecting systems, networks, and data from unauthorized access, damage, or theft.
Key term
Authorization
Authorization determines what an authenticated user is allowed to do within a system, such as accessing files, running programs, or changing settings.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.