This CAS-004 practice question tests your understanding of security engineering and 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.
A company is migrating from RSA to elliptic curve cryptography for digital signatures. They require a signature algorithm that provides at least 128 bits of security strength and is resistant to quantum computing attacks in the foreseeable future. Which TWO algorithms meet these requirements? (Select TWO.)
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "least"
Why it matters: You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
ECDSA P-256
Why wrong: P-256 provides 128-bit security but is less conservative than P-384.
DSA 3072
Why wrong: DSA is not elliptic curve and has larger key sizes.
Ed25519
Ed25519 provides 128-bit security and is resistant to known attacks.
RSA 4096
Why wrong: RSA is not elliptic curve cryptography.
ECDSA P-384
P-384 provides 192-bit security, exceeding 128 bits.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Ed25519
ECDSA P-384 provides 192-bit security, and Ed25519 provides 128-bit security. Both are EC-based. DSA 3072 is not EC. RSA 4096 is not EC. ECDSA P-256 provides 128-bit security but is less conservative.
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.
ECDSA P-256
Why it's wrong here
P-256 provides 128-bit security but is less conservative than P-384.
DSA 3072
Why it's wrong here
DSA is not elliptic curve and has larger key sizes.
Ed25519
Why this is correct
Ed25519 provides 128-bit security and is resistant to known attacks.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
RSA 4096
Why it's wrong here
RSA is not elliptic curve cryptography.
ECDSA P-384
Why this is correct
P-384 provides 192-bit security, exceeding 128 bits.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
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.
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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: Ed25519 — ECDSA P-384 provides 192-bit security, and Ed25519 provides 128-bit security. Both are EC-based. DSA 3072 is not EC. RSA 4096 is not EC. ECDSA P-256 provides 128-bit security but is less conservative.
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: "least". You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
Static NAT maps one inside address to one outside address.
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Last reviewed: Jul 4, 2026
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