CCP TLS, PKI & Encryption Standards 2 — Questions and Answers
Question 1: Which TLS extension allows a client to request a server to include a stapled OCSP response during the handshake?
- Certificate Transparency
- Status Request (OCSP Stapling) (Correct answer)
- Server Name Indication
- Extended Master Secret
Correct answer: Status Request (OCSP Stapling)
The TLS 'status_request' extension (RFC 6066) enables OCSP stapling, where the server attaches a cached OCSP response to reduce client-side revocation lookups.
Question 2: In a PKI hierarchy, what is the primary purpose of an intermediate CA rather than issuing end-entity certificates directly from the root CA?
- To improve certificate issuance speed
- To reduce the cryptographic key size required
- To protect the root CA private key by keeping it offline (Correct answer)
- To enable cross-certification between different PKIs
Correct answer: To protect the root CA private key by keeping it offline
Intermediate CAs allow the root CA to remain offline (air-gapped), so if an intermediate CA is compromised, only that CA's certificates need revocation, not the entire trust hierarchy.
Question 3: Which cipher suite component in TLS 1.2 provides forward secrecy?
- RSA key exchange
- AES-256-GCM encryption
- Ephemeral Diffie-Hellman (DHE or ECDHE) (Correct answer)
- SHA-384 MAC
Correct answer: Ephemeral Diffie-Hellman (DHE or ECDHE)
Ephemeral Diffie-Hellman key exchange generates a new key pair per session, so compromising the server's long-term key cannot decrypt previously captured traffic.
Question 4: What does Certificate Transparency (CT) primarily protect against?
- Weak cipher suites negotiated during TLS handshake
- Misissued or fraudulent certificates that CAs issue without domain owner knowledge (Correct answer)
- Expired certificates that servers fail to renew on time
- Private key theft from certificate stores
Correct answer: Misissued or fraudulent certificates that CAs issue without domain owner knowledge
CT requires CAs to log all issued certificates to public append-only logs, enabling domain owners and monitors to detect unauthorized or misissued certificates quickly.
Question 5: An attacker intercepts a TLS 1.3 handshake. Which of the following attacks is TLS 1.3 specifically designed to eliminate compared to TLS 1.2?
- Certificate pinning bypass
- Downgrade attacks using legacy cipher suites (Correct answer)
- Padding oracle attacks on AES-CBC
- DNS hijacking of OCSP responders
Correct answer: Downgrade attacks using legacy cipher suites
TLS 1.3 removed all weak and legacy cipher suites and handshake options, eliminating downgrade attack vectors like POODLE, BEAST, and DROWN that exploited TLS 1.2 fallback modes.
Question 6: Which X.509 certificate field is used to specify permitted and excluded DNS name subtrees in a CA certificate to constrain which domains it may issue certificates for?
- Key Usage
- Extended Key Usage
- Name Constraints (Correct answer)
- Subject Alternative Name
Correct answer: Name Constraints
The Name Constraints extension (critical) restricts the namespaces within which an intermediate CA may issue certificates, preventing it from signing certificates for unauthorized domains.
Question 7: When a TLS session is resumed using a pre-shared key (PSK) in TLS 1.3, what security property is potentially weakened?
- Confidentiality of the session data
- Authentication of the server identity
- Forward secrecy for the resumed session (Correct answer)
- Integrity checking via AEAD ciphers
Correct answer: Forward secrecy for the resumed session
PSK-only resumption reuses keying material from a prior session, so compromising that PSK can expose the resumed session's traffic, weakening forward secrecy.
CCP TLS, PKI & Encryption Standards 2
Which TLS extension allows a client to request a server to include a stapled OCSP response during the handshake?