Quick Answer
The answer is preimage resistance and collision resistance. Preimage resistance ensures that given a hash output, it is computationally infeasible to reverse-engineer any input that produces it, which directly protects the integrity of stored passwords or signed data. Collision resistance guarantees that no two distinct inputs can yield the same hash, preventing an attacker from substituting a fraudulent message for a legitimate one in digital signatures or message authentication codes. On the Systems Security Certified Practitioner SSCP exam, this question tests your understanding of the fundamental properties that distinguish a cryptographically secure hash from a simple checksum; a common trap is confusing second-preimage resistance with collision resistance, but remember that collision resistance is the stricter requirement. A useful memory tip is to think of the three pillars as “one-way, unique, and unpredictable,” where preimage resistance is the one-way property and collision resistance is the uniqueness guarantee.
This SSCP practice question tests your understanding of cryptography. 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.
Which TWO of the following are required properties of a cryptographically secure hash function? (Select exactly 2.)
Deterministic output
Why wrong: Determinism is a property but not a security requirement.
Collision resistance
It should be infeasible to find two different inputs with the same hash.
High speed for large inputs
Why wrong: Performance is a design goal but not a security property.
Low output entropy
Why wrong: High entropy is desired, not low.
Preimage resistance
Given a hash, it should be infeasible to find any input that produces it.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Collision resistance
Collision resistance (B) is a required property because it ensures that it is computationally infeasible to find two distinct inputs that produce the same hash output. Without this property, an attacker could substitute a legitimate message with a fraudulent one that yields an identical hash, breaking the integrity guarantees of the hash function. This is a fundamental requirement for digital signatures and message authentication codes (MACs) in cryptographic protocols.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Deterministic output
Why it's wrong here
Determinism is a property but not a security requirement.
Collision resistance
Why this is correct
It should be infeasible to find two different inputs with the same hash.
Related concept
Read the scenario before looking for a memorised answer.
High speed for large inputs
Why it's wrong here
Performance is a design goal but not a security property.
Low output entropy
Why it's wrong here
High entropy is desired, not low.
Preimage resistance
Why this is correct
Given a hash, it should be infeasible to find any input that produces it.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
ISC2 often tests the distinction between general hash function properties (like deterministic output) and the specific security properties required for cryptographic use, leading candidates to mistakenly select deterministic output as a required property when it is merely a basic characteristic of any hash function.
Detailed technical explanation
Preimage resistance (E) ensures that given a hash output, it is computationally infeasible to find any input that hashes to that value, which is critical for password storage and commitment schemes. Under the hood, these properties rely on the avalanche effect and the one-way nature of functions like SHA-256, where a single bit change in the input flips approximately half the output bits. In real-world scenarios, a failure of collision resistance (e.g., SHA-1's SHAttered attack) allowed attackers to create two different PDF files with the same hash, undermining certificate trust.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A security analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
What to study next
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FAQ
Cryptography — This question tests Cryptography — Read the scenario before looking for a memorised answer..
The correct answer is: Collision resistance — Collision resistance (B) is a required property because it ensures that it is computationally infeasible to find two distinct inputs that produce the same hash output. Without this property, an attacker could substitute a legitimate message with a fraudulent one that yields an identical hash, breaking the integrity guarantees of the hash function. This is a fundamental requirement for digital signatures and message authentication codes (MACs) in cryptographic protocols.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
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.
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