This CAS-004 practice question tests your understanding of security engineering and cryptography. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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, it was discovered that an application uses RSA with 1024-bit keys for encrypting sensitive data. The organization's security policy mandates a minimum of 128-bit symmetric equivalent security. Which of the following should be recommended as a replacement?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
RSA with 3072-bit keys
RSA 3072 provides 128-bit security, meeting the requirement.
AES-256-GCM
Why wrong: AES-256-GCM is a symmetric cipher, not an asymmetric replacement for RSA encryption.
ECDSA P-384
Why wrong: ECDSA is for digital signatures, not encryption.
RSA with 2048-bit keys
Why wrong: RSA 2048 provides about 112-bit security, below the 128-bit requirement.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
RSA with 3072-bit keys
RSA 2048 provides approximately 112-bit security, while RSA 3072 provides 128-bit. AES-256-GCM is symmetric, not asymmetric. ECDSA is for signatures, not encryption. So RSA 3072 is the correct choice.
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
For each option: why learners choose it and why it is or isn't the right answer here.
RSA with 3072-bit keys
Why this is correct
RSA 3072 provides 128-bit security, meeting the requirement.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
AES-256-GCM
Why it's wrong here
AES-256-GCM is a symmetric cipher, not an asymmetric replacement for RSA encryption.
ECDSA P-384
Why it's wrong here
ECDSA is for digital signatures, not encryption.
RSA with 2048-bit keys
Why it's wrong here
RSA 2048 provides about 112-bit security, below the 128-bit requirement.
Common exam traps
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
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.
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
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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 CAS-004 NAT questions on configuration and troubleshooting.
Security Engineering and Cryptography — study guide chapter
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FAQ
Security Engineering and Cryptography — This question tests Security Engineering and Cryptography — Static NAT maps one inside address to one outside address..
The correct answer is: RSA with 3072-bit keys — RSA 2048 provides approximately 112-bit security, while RSA 3072 provides 128-bit. AES-256-GCM is symmetric, not asymmetric. ECDSA is for signatures, not encryption. So RSA 3072 is the correct choice.
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 CAS-004 NAT questions on configuration and troubleshooting.
Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Static NAT maps one inside address to one outside address.
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Last reviewed: Jul 4, 2026
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