SSCP Cryptography Practice Question
A company wants to implement a key management system. They need to generate cryptographic keys that are unpredictable. Which source of randomness should be used?
⚠ Common exam trap
ISC2 SSCP often tests the misconception that a PRNG seeded with a timestamp is sufficient for cryptography, but the trap is that timestamps are predictable or guessable, making the output deterministic and insecure for key generation.
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
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Hardware random number generator (HRNG)
A hardware random number generator (HRNG) is the correct choice because it derives randomness from physical processes (e.g., thermal noise, quantum effects) that are inherently unpredictable and non-deterministic. Cryptographic key generation requires true entropy to resist brute-force and prediction attacks, which software-based deterministic methods cannot guarantee.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Hardware random number generator (HRNG)
Why this is correct
An HRNG derives randomness from a physical entropy source, such as thermal or quantum noise, so its output cannot be predicted or reproduced. This satisfies the requirement for unpredictable key material, unlike deterministic software PRNGs, whose sequences are reproducible once the seed is known.
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Random numbers from a website
Why it's wrong here
A website supplies no verifiable entropy source and exposes keys to network interception, tampering and provider logging, so outputs cannot be trusted as unpredictable. Fetching random values online is tempting for convenience in non-security contexts such as picking lottery numbers for a demo.
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Linear congruential generator (LCG)
Why it's wrong here
A linear congruential generator is deterministic and its output is predictable once the seed and parameters are known, so it cannot supply unpredictable keys. It is tempting because LCGs are fast and simple for simulations, but cryptographic key generation demands a cryptographically secure pseudorandom number generator seeded from a high-entropy source.
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Pseudorandom number generator (PRNG) seeded with current timestamp
Why it's wrong here
Seeding a PRNG with the current timestamp gives an attacker a tiny, guessable seed space, so the generated key stream can be reproduced by brute-forcing plausible times. Timestamp seeding suits reproducible test data or simulations, not cryptographic key generation.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SSCP 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 SSCP exam.