SE Cryptography and PKI 3

Question 1

In a PKI hierarchy, what is the role of an Intermediate CA?

Accepted Answer

It issues end-entity certificates, insulating the Root CA from direct exposure

Answer

Intermediate CAs sit between the Root CA and end-entity certificates, allowing the Root CA to be kept offline and reducing risk if the Intermediate is compromised.

Question 2

What is the purpose of salting a password before hashing?

Accepted Answer

Prevent precomputed (rainbow table) attacks by making each hash unique

Answer

A salt is a random value added to the password before hashing, ensuring identical passwords produce different hashes and defeating precomputed table attacks.

Question 3

Which cipher mode of operation provides both confidentiality and integrity in a single pass?

Accepted Answer

GCM (Galois/Counter Mode)

Answer

AES-GCM is an authenticated encryption mode that simultaneously provides confidentiality (counter mode encryption) and data integrity (GHASH authentication tag).

Question 4

What does certificate pinning accomplish in a mobile application?

Accepted Answer

Restricts the app to accept only specific certificates, preventing MITM via rogue CAs

Answer

Certificate pinning hardcodes the expected certificate or public key so the app rejects connections using any other certificate, even if signed by a trusted CA.

Question 5

An attacker collects two different messages that produce the same hash value. What type of cryptographic attack is this?

Accepted Answer

Birthday (collision) attack

Answer

A collision attack finds two distinct inputs with the same hash output, exploiting the birthday paradox in hash function design.

SE - Security Engineer Practice Test

SE - Security Engineer Practice Test

SE Cryptography and PKI 3