Quick Answer
The answer is constant time comparison, along with salting and computational slowness, as the three critical characteristics of a password hashing algorithm. Constant time comparison prevents timing attacks by ensuring that the hash comparison operation takes the same amount of time regardless of how many characters match, eliminating a side-channel that could reveal the correct hash byte by byte. On the SSCP exam, this concept tests your understanding of secure authentication implementation beyond just hashing theory—a common trap is confusing “fast” hashing (like MD5) with secure hashing, when in fact algorithms must be deliberately slow (e.g., bcrypt, PBKDF2) to resist brute-force attacks. Salting, as the explanation notes, ensures unique hashes even for identical passwords, thwarting rainbow tables. Remember the mnemonic “SCS” for Slow, Constant-time, Salted—if any of these is missing, the algorithm is not fit for password storage.
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 THREE characteristics are important for a password hashing algorithm?
Fixed output length
Why wrong: Fixed output length is a property but not a security characteristic.
Salt usage
Salt prevents rainbow table attacks.
Reversible
Why wrong: Hashing should be one-way, not reversible.
Slow computation
Slowness increases the cost of brute-force attacks.
Constant time comparison
Constant time comparison prevents timing side-channel attacks.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Salt usage
B is correct because salting ensures that each password hash is unique even if two users have the same password, preventing precomputed rainbow table attacks. A salt is a random value concatenated with the password before hashing, and it must be stored alongside the hash for verification.
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.
Fixed output length
Why it's wrong here
Fixed output length is a property but not a security characteristic.
Salt usage
Why this is correct
Salt prevents rainbow table attacks.
Related concept
Read the scenario before looking for a memorised answer.
Reversible
Why it's wrong here
Hashing should be one-way, not reversible.
Slow computation
Why this is correct
Slowness increases the cost of brute-force attacks.
Related concept
Read the scenario before looking for a memorised answer.
Constant time comparison
Why this is correct
Constant time comparison prevents timing side-channel attacks.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
ISC2 often tests the misconception that fixed output length is a key requirement for password hashing, when in fact it is a generic property of all hash functions and not specific to password storage security.
Trap categories for this question
Command / output trap
Fixed output length is a property but not a security characteristic.
Detailed technical explanation
Modern password hashing algorithms like bcrypt, PBKDF2, and Argon2 are designed with a configurable work factor (cost) to slow down brute-force attempts. Constant-time comparison (option E) is critical to prevent timing side-channel attacks where an attacker can deduce the correct hash by measuring response times during comparison; this is implemented using functions like `hash_equals()` in PHP or `MessageDigest.isEqual()` in Java.
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: Salt usage — B is correct because salting ensures that each password hash is unique even if two users have the same password, preventing precomputed rainbow table attacks. A salt is a random value concatenated with the password before hashing, and it must be stored alongside the hash for verification.
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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