CAS-004 Security Engineering Practice Test 7 — 15 Questions

Question 1

A security engineer is reviewing a TLS 1.3 configuration. Which of the following is a key feature of TLS 1.3 that improves security compared to earlier versions?

Accepted Answer

Mandatory forward secrecy using ephemeral Diffie-Hellman. TLS 1.3 mandates forward secrecy by requiring ephemeral Diffie-Hellman key exchange (DHE or ECDHE), which ensures that session keys cannot be recovered even if the server's long-term private key is later compromised. This is a core security improvement over TLS 1.2, where static RSA key exchange was allowed and lacked forward secrecy.

Answer

Support for RC4 cipher suite

Answer

Support for static RSA key exchange

Answer

Ability to downgrade to TLS 1.2

Question 2

An organization is setting up a PKI with a three-tier hierarchy (root CA, issuing CA, and registration authority). Which TWO of the following are best practices for securing the root CA?

Accepted Answer

Keep the root CA offline and physically secured. Option D is correct because the root CA should be kept offline and physically secured so its private key is never exposed to network-based attacks; it is only brought online for rare operations such as signing the issuing CA's certificate. Option E is correct because storing the root CA private key in a hardware security module (HSM) protects it with tamper-resistant hardware, enforces key non-exportability, and supports secure cryptographic operations. Option A is wrong because exposing the root CA to the network for certificate requests increases its attack surface and violates the offline-root best practice. Option B is wrong because CRL distribution points belong on the issuing CA (and end-entity certificates), not on the offline root CA. Option C is wrong because end-entity certificates should be issued by the issuing CA, not directly by the root CA, to preserve the hierarchy and limit root key exposure.

Answer

Allow the root CA to be accessible over the network for certificate requests

Answer

Enable CRL distribution points on the root CA

Answer

Use the root CA to issue end-entity certificates directly

Question 3

An IoT device uses a Trusted Platform Module (TPM) 2.0 for secure boot and attestation. Which THREE of the following functions does the TPM provide to support these security features?

Accepted Answer

Platform Configuration Registers (PCRs) for storing measurements. Option B is correct because TPM 2.0 provides Platform Configuration Registers (PCRs), which are shielded registers used to store cryptographic measurements (hashes) of firmware, boot loaders, and OS components during secure boot, forming the basis for integrity verification. Option D is correct because sealed storage binds a decryption key to specific PCR values, so the protected data can only be unsealed when the platform's measurements match the expected known-good state, enforcing secure boot integrity. Option E is correct because remote attestation relies on the TPM_Quote command, which signs the current PCR values with an Attestation Identity Key (AIK) so a remote verifier can confirm the device's boot state. Option A is not correct because TPM 2.0 is not designed for accelerated bulk symmetric encryption; it only offers limited cryptographic operations and is far too slow for that purpose. Option C is not correct because, although TPM 2.0 includes a hardware random number generator, it is not one of the functions specifically supporting secure boot and attestation as described in this scenario.

Answer

Accelerated symmetric encryption

Answer

Hardware random number generation

Question 4

A security assessor is evaluating an application that uses ChaCha20-Poly1305 for encryption. Which TWO of the following are true about this cryptographic algorithm?

Accepted Answer

It is a stream cipher. Option C is correct because ChaCha20 is a stream cipher: it generates a keystream from a 256-bit key and a 96-bit nonce (with a 32-bit counter) and XORs it with the plaintext, so no block structure is involved. Option D is correct because the Poly1305 one-time authenticator is combined with ChaCha20 to form an AEAD construction, producing a 128-bit authentication tag that protects both the ciphertext and any additional authenticated data (AAD) such as headers. Option A is wrong because ChaCha20 is unrelated to AES; it was designed by Daniel J. Bernstein as a variant of Salsa20 and does not use the Rijndael/AES structure or S-boxes. Option B is wrong because stream ciphers encrypt data byte-by-byte and require no padding to reach a block size. Option E is wrong because ChaCha20 is not a block cipher; it processes data as a continuous keystream rather than fixed-size blocks.

Answer

It is based on the AES algorithm

Answer

It requires padding to achieve correct block sizes

Answer

It is a block cipher

Question 5

A security architect is designing a VPN that requires both authentication and encryption. Which IPsec protocol provides both services in a single protocol?

Accepted Answer

ESP in tunnel mode. ESP provides both encryption and optional authentication, while AH only provides authentication without encryption.

Answer

AH in transport mode

Answer

IKEv2

Answer

AH in tunnel mode

Question 6

An organization wants to implement a hardware root of trust for measuring system integrity at boot. Which technology should be used to store measurements in Platform Configuration Registers (PCRs) and support remote attestation?

Accepted Answer

TPM 2.0. TPM 2.0 provides PCRs for measured boot and supports attestation, making it suitable for hardware root of trust.

Answer

HSM

Answer

Secure Enclave

Answer

UEFI Secure Boot

Question 7

An organization requires a cryptographic algorithm that provides both encryption and authentication in a single pass. Which algorithm should be selected?

Accepted Answer

AES-256-GCM. AES-256-GCM (Galois/Counter Mode) is an authenticated encryption with associated data (AEAD) algorithm that provides both confidentiality (encryption) and integrity/authentication in a single pass. It combines AES counter mode encryption with GHASH for authentication, making it efficient and secure. This meets the requirement for a single algorithm that does both.

Answer

AES-256-CBC

Answer

SHA-256

Answer

RSA 4096

Question 8

A company is implementing a passwordless authentication solution using FIDO2/WebAuthn. What is the primary security advantage of this approach over traditional password-based authentication?

Accepted Answer

It prevents phishing attacks by using cryptographic keys.. FIDO2/WebAuthn uses public-key cryptography where the private key never leaves the authenticator (e.g., a security key or platform authenticator), and the origin is cryptographically bound to the credential. This origin binding means a phishing site with a different domain cannot trigger the authenticator to sign the challenge, effectively preventing credential phishing. Traditional passwords, by contrast, can be captured and replayed by phishing proxies.

Answer

It allows users to share passwords securely.

Answer

It reduces server storage requirements.

Answer

It eliminates the need for multi-factor authentication.

Question 9

Which key exchange algorithm provides perfect forward secrecy (PFS) and is recommended for use in TLS 1.3?

Accepted Answer

ECDHE. ECDHE (Elliptic Curve Diffie-Hellman Ephemeral) provides PFS as session keys are ephemeral.

Answer

RSA key exchange

Answer

Pre-shared key (PSK)

Answer

Diffie-Hellman (DH)

Question 10

An IoT device manufacturer wants to ensure secure firmware updates. Which approach best protects against malicious firmware being installed on devices?

Accepted Answer

Digitally sign the firmware with a private key. Code signing with a trusted key ensures only authorized firmware can be installed.

Answer

Compress the firmware to reduce size

Answer

Use a hash of the firmware for integrity verification

Answer

Encrypt the firmware with a symmetric key

Question 11

A security architect is designing a system that requires hardware-enforced isolation for sensitive computations. Which technology provides the strongest isolation by running code in a protected environment within the CPU?

Accepted Answer

Intel SGX. Intel SGX provides enclaves that isolate code and data even from the operating system, offering strong hardware isolation.

Answer

HSM

Answer

TPM 2.0

Answer

ARM TrustZone

Question 12

A company is implementing a Privileged Access Management (PAM) solution to manage admin credentials. Which feature allows administrators to request temporary elevated access for a specific task?

Accepted Answer

Just-in-time access. Just-in-time (JIT) access is a core PAM capability that grants elevated privileges only when needed, for a limited time, and often with approval workflows. It directly addresses the requirement for temporary elevated access for a specific task, reducing standing privileges and the attack surface. JIT typically integrates with identity governance to enforce least privilege and just-enough administration.

Answer

Session recording

Answer

Password vaulting

Answer

Break-glass accounts

Question 13

A company is evaluating multi-factor authentication methods. Which TWO are considered phishing-resistant? (Select TWO.)

Accepted Answer

FIDO2/WebAuthn. FIDO2/WebAuthn (A) is phishing-resistant because it uses public-key cryptography bound to the origin (relying party ID), so credentials created for one site cannot be replayed on a look-alike phishing domain. Hardware security tokens such as a YubiKey (E) are phishing-resistant for the same reason: they implement FIDO2/U2F and sign a challenge with a private key tied to the legitimate origin, and the private key never leaves the device. In contrast, biometric authentication on a smartphone (B) is only a local verification factor and, by itself, is not bound to the web origin, so it can be captured or relayed in a phishing flow. TOTP via a mobile app (C) is a shared-secret code that a phishing site can proxy in real time, so it is not phishing-resistant. SMS one-time codes (D) are similarly replayable and additionally vulnerable to SIM-swapping and interception, making them the weakest option here.

Answer

Biometric authentication on a smartphone

Answer

TOTP via mobile app

Answer

SMS one-time codes

Question 14

A security architect is designing a new authentication system for a cloud-based application that requires strong multi-factor authentication. The solution must be resistant to phishing attacks and not rely on shared secrets. Which of the following is the BEST choice?

Accepted Answer

FIDO2/WebAuthn. FIDO2/WebAuthn is a passwordless authentication protocol that uses public key cryptography and is resistant to phishing because the private key never leaves the user's device.

Answer

HOTP with a hardware token

Answer

TOTP via a mobile authenticator app

Answer

SMS one-time passcodes

Question 15

A network administrator needs to establish a secure VPN tunnel between two branch offices using IPsec. The requirement is to encrypt the entire IP packet, including the original IP header. Which IPsec mode should be used?

Accepted Answer

Tunnel mode. Tunnel mode encrypts the entire IP packet and adds a new IP header, making it suitable for VPNs between networks.

Answer

AH mode

Answer

IKEv1

Answer

Transport mode