Question 210
After a prior digital signatures finding, a payment-services company reports that the approved safeguard is implemented: “Verify a digital signature against a trusted signer public key and valid trust state.” The assurance team must decide whether this measure demonstrably works in operation. Which evidence would MOST directly establish its effectiveness?
- Use the completion of this alternative as proof: Use a plain checksum as signer authentication
- Corrupt a signed artifact and verify the signature check fails
- Accept a signed change ticket saying: Verify a digital signature against a trusted signer public key and valid trust state
- Run this adjacent but different test as the sole proof: Inventory cryptographic dependencies and test approved hybrid or migration pathways
Explanation
Correct Answer
B:Tamper rejection supports integrity and authenticity.
Incorrect Answers
A:Checksums lack private-key origin proof. Corrupt a signed artifact and verify the signature check fails.
C:Corrupt a signed artifact and verify the signature check fails. Tamper rejection supports integrity and authenticity.
D:Agility evidence supports a phased transition. It tests postquantum, while this case requires evidence about digital signatures.
Question 211
An analyst knows several plaintext/ciphertext pairs and is trying to recover a secret key. Which response best addresses the central security requirement with a defensible, risk-based design?
- Recognize a known-plaintext attack and evaluate cipher strength under that threat model
- Treat the attack as an unauthenticated network flood
- Describe the situation only as brute-force search of every key
- Defend against chosen-ciphertext/oracle attacks using authenticated encryption and uniform failure handling
Explanation
Correct Answer
A:An attacker need not choose plaintext to exploit exposed known pairs.
Incorrect Answers
B:Availability flooding is not ciphertext analysis.
C:Known text supplies additional structure beyond exhaustive guesses.
D:Adaptive decryption feedback can leak information without giving the key directly. Recognize a known-plaintext attack and evaluate cipher strength under that threat model.
Question 212
A decryption API returns distinct errors when an attacker submits modified ciphertext repeatedly. Which response best addresses the central security requirement with a defensible, risk-based design?
- Assume encryption alone prevents malleability
- Defend against chosen-ciphertext/oracle attacks using authenticated encryption and uniform failure handling
- Use constant-time comparison for sensitive authenticator values
- Publish detailed padding failure responses
Explanation
Correct Answer
B:Adaptive decryption feedback can leak information without giving the key directly.
Incorrect Answers
A:Unauthenticated modes can be altered.
C:Timing differences can leak information about secret prefixes. Defend against chosen-ciphertext/oracle attacks using authenticated encryption and uniform failure handling.
D:Distinct errors can aid oracle exploitation.
Question 213
A secret comparison routine returns earlier for wrong first-byte guesses. Which response best addresses the central security requirement with a defensible, risk-based design?
- Defend against chosen-ciphertext/oracle attacks using authenticated encryption and uniform failure handling
- Use constant-time comparison for sensitive authenticator values
- Add a longer random delay after comparison
- Use ordinary string equality and keep network TLS
Explanation
Correct Answer
B:Timing differences can leak information about secret prefixes.
Incorrect Answers
A:Adaptive decryption feedback can leak information without giving the key directly. Use constant-time comparison for sensitive authenticator values.
C:Noise does not reliably eliminate data-dependent behavior.
D:TLS does not remove local timing side channels.
Question 214
A shared processor leaks cryptographic secret information through cache contention. Which response best addresses the central security requirement with a defensible, risk-based design?
- Increase encryption key size alone
- Enforce rate limits, account risk controls and strong authentication
- Limit sensitive cross-tenant resource sharing and use hardened implementations appropriate to the side channel
- Move the same vulnerable code to another virtual machine on the same host
Explanation
Correct Answer
C:Physical microarchitectural behavior can expose secrets outside algorithm design.
Incorrect Answers
A:More bits do not fix information leakage.
B:Online guess throttling restricts feasible search regardless of password complexity. Limit sensitive cross-tenant resource sharing and use hardened implementations appropriate to the side channel.
D:Shared hardware may retain the same side channel.
Question 215
An attacker can make unlimited online password guesses against a login service. Which response best addresses the central security requirement with a defensible, risk-based design?
- Display CAPTCHA text but leave an unrestricted API authentication path
- Show a longer password policy without limiting online attempts
- Enforce rate limits, account risk controls and strong authentication
- Limit sensitive cross-tenant resource sharing and use hardened implementations appropriate to the side channel
Explanation
Correct Answer
C:Online guess throttling restricts feasible search regardless of password complexity.
Incorrect Answers
A:Attackers may bypass frontend-only checks.
B:Long passwords help but do not alone prevent abuse of weak accounts.
D:Physical microarchitectural behavior can expose secrets outside algorithm design. Enforce rate limits, account risk controls and strong authentication.
Question 216
A secure device reveals unexpected key information when power is glitched during signing. Which response best addresses the central security requirement with a defensible, risk-based design?
- Use constant-time comparison for sensitive authenticator values
- Add tamper/fault detection and fault-resistant implementation measures
- Increase network firewall throughput
- Assume ordinary logical input validation blocks power manipulation
Explanation
Correct Answer
B:Induced faults can alter computation to reveal cryptographic material.
Incorrect Answers
A:Timing differences can leak information about secret prefixes. Add tamper/fault detection and fault-resistant implementation measures.
C:A firewall does not protect device power-glitch attacks.
D:Physical faults bypass normal input routes.
Question 217
After a prior known plaintext finding, a regional hospital network reports that the approved safeguard is implemented: “Recognize a known-plaintext attack and evaluate cipher strength under that threat model.” The assurance team must decide whether this measure demonstrably works in operation. Which evidence would MOST directly establish its effectiveness?
- Accept a signed change ticket saying: Recognize a known-plaintext attack and evaluate cipher strength under that threat model
- Use the completion of this alternative as proof: Describe the situation only as brute-force search of every key
- Check the cryptosystem's resistance under known-plaintext test vectors
- Run this adjacent but different test as the sole proof: Submit malformed ciphertext and verify uniform authenticated failure
Explanation
Correct Answer
C:Correct model selection drives cryptanalytic assurance.
Incorrect Answers
A:Check the cryptosystem's resistance under known-plaintext test vectors. Correct model selection drives cryptanalytic assurance.
B:Known text supplies additional structure beyond exhaustive guesses. Check the cryptosystem's resistance under known-plaintext test vectors.
D:Oracle resistance needs negative tests. It tests chosen ciphertext, while this case requires evidence about known plaintext.
Question 218
A data center proposal is adjacent to a floodplain and relies on one access road. Which response best addresses the central security requirement with a defensible, risk-based design?
- Evaluate environmental, utility, logistics and geographic threats before site selection
- Choose solely by rent price
- Design seismic anchoring and business continuity measures for credible local hazards
- Assume backups remove every site hazard
Explanation
Correct Answer
A:Physical location can create correlated outages and recovery obstacles.
Incorrect Answers
B:Cost does not capture flood or isolation risk.
C:Natural hazard resilience requires facility-specific mitigations. Evaluate environmental, utility, logistics and geographic threats before site selection.
D:Recovery still depends on physical access and utilities.
Question 219
A facility near seismic faults has unsecured equipment racks. Which response best addresses the central security requirement with a defensible, risk-based design?
- Add additional logical passwords to the racks
- Evaluate environmental, utility, logistics and geographic threats before site selection
- Design seismic anchoring and business continuity measures for credible local hazards
- Ignore site-specific hazard because equipment is insured
Explanation
Correct Answer
C:Natural hazard resilience requires facility-specific mitigations.
Incorrect Answers
A:Passwords do not prevent toppling.
B:Physical location can create correlated outages and recovery obstacles. Design seismic anchoring and business continuity measures for credible local hazards.
D:Insurance does not maintain service or protect people.
Question 220
Visitors can walk directly from a public lobby into the server hall. Which response best addresses the central security requirement with a defensible, risk-based design?
- Layer physical zones and enforce authorized transitions using badges, locks and monitoring
- Use only a sign saying Authorized Personnel
- Provide resilient HVAC, environmental monitoring and controlled shutdown procedures
- Give all visitors unrestricted temporary badges
Explanation
Correct Answer
A:Physical defense in depth separates public, controlled and restricted areas.
Incorrect Answers
B:Signs do not prevent entry.
C:Environmental resilience needs capacity and response, not alerts alone. Layer physical zones and enforce authorized transitions using badges, locks and monitoring.
D:Unscoped access defeats zoning.
Certified Information Systems Security Professional (CISSP) Practice Tests