The correct recommendation is to migrate to a widely-accepted encryption standard such as AES. This is because custom encryption algorithms carry severe risks, as they lack the extensive peer review, cryptanalysis, and public testing that standards like AES have undergone for decades. Even if a developer claims better efficiency, the absence of proven security guarantees against known attack vectors—such as differential or linear cryptanalysis—makes the application vulnerable, especially for protecting sensitive financial data. On the CISSP exam, this scenario tests your understanding of the cryptographic lifecycle and the principle that security through obscurity is never acceptable; a common trap is accepting performance claims over verifiable security. Remember the mnemonic “Don’t Roll Your Own Crypto”—if it hasn’t survived the crucible of global cryptanalysis, it’s not ready for production.
CISSP Security Assessment and Testing Practice Question
This CISSP practice question tests your understanding of security assessment and testing. 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.
During a security audit of a financial application, the auditor discovers that the application uses a custom encryption algorithm for storing sensitive data. The developer claims it is more efficient than AES. What should the auditor recommend?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Migrate to a widely-accepted encryption standard such as AES
Custom encryption algorithms are highly risky because they have not undergone the extensive peer review and cryptanalysis that standards like AES have. Even if the developer claims better efficiency, the lack of proven security guarantees makes the application vulnerable to attacks. The correct recommendation is to migrate to a widely-accepted standard such as AES, which is FIPS 197 validated and trusted for protecting sensitive financial data.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Conduct additional penetration testing on the encryption implementation
Why it's wrong here
Testing cannot guarantee security of a custom algorithm.
✗
Accept the risk if the algorithm is more efficient
Why it's wrong here
Efficiency does not justify security risk.
✗
Perform a cryptoanalysis of the algorithm to validate its strength
Why it's wrong here
Even if valid, custom algorithms are not recommended for production.
✓
Migrate to a widely-accepted encryption standard such as AES
Why this is correct
Standard algorithms are extensively reviewed and trusted.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may think performing cryptanalysis (Option C) is a valid audit recommendation, but in practice, the auditor's role is to enforce the use of proven standards, not to validate unproven custom cryptography.
Detailed technical explanation
How to think about this question
AES (Advanced Encryption Standard) is a symmetric block cipher standardized by NIST in FIPS 197, using key sizes of 128, 192, or 256 bits, and has withstood years of global cryptanalysis. Custom algorithms often lack diffusion and confusion properties, making them susceptible to linear and differential cryptanalysis. In a real-world scenario, a financial application using a custom cipher could have its encrypted data decrypted by an attacker with moderate resources, leading to massive data breach liabilities.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CISSP question in full detail.
Security Assessment and Testing — This question tests Security Assessment and Testing — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Migrate to a widely-accepted encryption standard such as AES — Custom encryption algorithms are highly risky because they have not undergone the extensive peer review and cryptanalysis that standards like AES have. Even if the developer claims better efficiency, the lack of proven security guarantees makes the application vulnerable to attacks. The correct recommendation is to migrate to a widely-accepted standard such as AES, which is FIPS 197 validated and trusted for protecting sensitive financial data.
What should I do if I get this CISSP question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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