312-50 Question 473
Select 3▪ Cryptography Attack CountermeasuresA financial services company discovers that several internal web applications still accept TLS 1.0 and a small set of CBC-mode cipher suites for compatibility with legacy clients. During an assessment, an ethical hacker notes that an attacker positioned on the same network segment could attempt downgrade and padding-oracle-style attacks against weak protocol and cipher configurations. The company wants to reduce the practical risk of cryptographic attacks without redesigning the applications immediately. Which THREE countermeasures should the security team implement first?
- A
Disable TLS 1.0/1.1 and weak cipher suites, and enforce only strong protocol versions and modern cipher suites such as TLS 1.2/1.3 with AEAD ciphers
- B
Enable HTTP Strict Transport Security (HSTS) and redirect all HTTP traffic to HTTPS to reduce downgrade opportunities from plaintext access paths
- C
Replace all server certificates monthly regardless of key length, CA trust, or protocol configuration
- D
Disable insecure renegotiation/compression where applicable and prioritize forward-secret cipher suites to reduce exposure to known TLS attack classes
- E
Increase RSA key size to 8192 bits while continuing to permit legacy TLS 1.0 CBC suites for compatibility
Show answer and explanation
Correct answers: A, B, D
Explanation
The best answer is to remove obsolete TLS versions and weak cipher suites, enforce HTTPS-only access behavior with HSTS, and disable legacy TLS features while preferring forward-secret configurations. In real-world cryptography attack countermeasures, protocol and cipher selection matter more than simply increasing key sizes or rotating certificates on an arbitrary schedule. Current industry guidance from sources such as NIST SP 800-52 Rev. 2 recommends TLS 1.2 or later, and modern operational guidance from OWASP Transport Layer Protection and the IETF TLS community strongly favors AEAD cipher suites and the elimination of deprecated protocol versions. HSTS is also a widely accepted best practice to reduce downgrade and SSL-stripping opportunities. Together, these measures provide meaningful, practical risk reduction without requiring an immediate application rewrite.
- A. Correct.
Correct. The most effective immediate countermeasure is to remove obsolete protocol versions and weak cipher suites. TLS 1.0 and 1.1 are deprecated by current best practice, and CBC-based suites have a history of practical weaknesses in certain TLS contexts. Enforcing TLS 1.2 or TLS 1.3 with AEAD suites such as AES-GCM or ChaCha20-Poly1305 directly reduces exposure to downgrade, padding-oracle, and related cryptographic attacks. This is a standard hardening step in production environments.
- B. Correct.
Correct. HSTS helps prevent protocol downgrade from HTTPS to HTTP by instructing compliant browsers to use HTTPS only for a site after the first secure visit, and preload can strengthen this further. While HSTS does not fix weak TLS configuration by itself, it is an important countermeasure against SSL stripping and plaintext downgrade paths, which is relevant when an attacker is on-path and attempting to force weaker communication methods.
- C. Incorrect.
Incorrect. Frequent certificate replacement does not address the root issue in this scenario. The problem is acceptance of obsolete TLS versions and weak cipher suites, not certificate age. Rotating certificates can be useful for lifecycle management or after compromise, but doing so monthly without changing protocol and cipher policy provides little protection against downgrade or CBC-related attacks.
- D. Correct.
Correct. Disabling TLS compression and insecure renegotiation where relevant helps mitigate known attack classes such as CRIME and renegotiation-related issues in legacy deployments. Prioritizing forward-secret suites, typically ECDHE-based in TLS 1.2, limits the impact of private-key compromise on past sessions. Although TLS 1.3 handles many of these concerns by design, this is still a practical hardening step for environments that must maintain TLS 1.2 during transition.
- E. Incorrect.
Incorrect. Larger RSA keys do not compensate for weak protocol choices. Continuing to allow legacy TLS 1.0 with CBC suites leaves the environment exposed to the same practical attack surface. Increasing key size may increase computational overhead and does not meaningfully mitigate downgrade or padding-oracle-style risks arising from outdated TLS configuration.