- A
The hash function SHA-256 provides insufficient collision resistance for the order volume.
Why wrong: SHA-256 collision resistance is strong; collisions are astronomically unlikely.
- B
The use of a fixed seed for key generation leads to weak keys, making it possible for an attacker to forge signatures.
Why wrong: Weak keys enable forgery, not signature collisions.
- C
The private key is reused across multiple instances, causing storage conflicts.
Why wrong: Key reuse does not cause signature collisions; it could lead to key compromise if one instance is breached.
- D
The signature algorithm does not use a random salt or padding, causing deterministic signatures that can collide when the same order is processed twice.
Deterministic signatures produce the same output for the same input; if two orders have identical hashes (e.g., due to data equality or collision), they yield identical signatures.
Quick Answer
The answer is the signature algorithm does not use a random salt or padding, causing deterministic signatures that can collide when the same order is processed twice. This occurs because RSA without probabilistic padding, such as RSA-PSS, produces the same output for identical inputs, meaning if two orders generate the same hash—whether through a hash collision or identical order data—the signature will be identical, breaking non-repudiation. On the CISSP exam, this scenario tests your understanding of digital signature collision deterministic algorithm weaknesses, often disguised as a key generation or hash function problem. A common trap is blaming the fixed-seed key generation, but that weakens key entropy, not signature uniqueness. Remember: deterministic signatures need randomization; RSA-PSS adds a random salt to prevent collisions. Memory tip: “PSS = Padded, Salted, Safe.”
CISSP Software Development Security Practice Question
This CISSP practice question tests your understanding of software development security. 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 financial institution has developed a trading application that sends orders via an internal API. The application processes high-frequency trades and must ensure non-repudiation of orders. The development team implemented digital signatures using RSA with SHA-256. However, testers found that occasionally two different orders produce the same signature. The team suspects a collision resistance issue. After reviewing the implementation, they notice that the private key is generated using a deterministic key generation algorithm that uses a fixed seed derived from the current timestamp. The signatures are generated by signing the order hash directly. What is the most likely root cause of the signature collision?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
The signature algorithm does not use a random salt or padding, causing deterministic signatures that can collide when the same order is processed twice.
The signature algorithm does not include randomization (e.g., no random padding like in RSA-PSS), so the signature is deterministic. If two different orders produce the same hash (due to a collision or identical order data), they will have the same signature. While key generation with a fixed seed weakens the key, it does not cause signature collisions directly. The hash function is unlikely to be the issue. Key reuse across instances is not described.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The hash function SHA-256 provides insufficient collision resistance for the order volume.
Why it's wrong here
SHA-256 collision resistance is strong; collisions are astronomically unlikely.
- ✗
The use of a fixed seed for key generation leads to weak keys, making it possible for an attacker to forge signatures.
Why it's wrong here
Weak keys enable forgery, not signature collisions.
- ✗
The private key is reused across multiple instances, causing storage conflicts.
Why it's wrong here
Key reuse does not cause signature collisions; it could lead to key compromise if one instance is breached.
- ✓
The signature algorithm does not use a random salt or padding, causing deterministic signatures that can collide when the same order is processed twice.
Why this is correct
Deterministic signatures produce the same output for the same input; if two orders have identical hashes (e.g., due to data equality or collision), they yield identical signatures.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CISSP NAT questions on configuration and troubleshooting.
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FAQ
Questions learners often ask
What does this CISSP question test?
Software Development Security — This question tests Software Development Security — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The signature algorithm does not use a random salt or padding, causing deterministic signatures that can collide when the same order is processed twice. — The signature algorithm does not include randomization (e.g., no random padding like in RSA-PSS), so the signature is deterministic. If two different orders produce the same hash (due to a collision or identical order data), they will have the same signature. While key generation with a fixed seed weakens the key, it does not cause signature collisions directly. The hash function is unlikely to be the issue. Key reuse across instances is not described.
What should I do if I get this CISSP question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CISSP NAT questions on configuration and troubleshooting.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
About these practice questions
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Last reviewed: Jun 24, 2026
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.
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