CREST Cryptography & PKI

Question 1

Which cryptographic algorithm is considered asymmetric and commonly used for key exchange in TLS?

Accepted Answer

RSA

Answer

AES

Answer

SHA-256

Answer

3DES

Question 2

What is the primary purpose of a Certificate Authority (CA) in PKI?

Accepted Answer

To issue and sign digital certificates

Answer

To encrypt network traffic

Answer

To store private keys for users

Answer

To hash passwords

Question 3

Which of the following describes a collision attack against a hash function?

Accepted Answer

Finding two different inputs that produce the same hash output

Answer

Reversing a hash back to its original input

Answer

Brute-forcing a hash to find the plaintext

Answer

Injecting data into a hashed message

Question 4

What does perfect forward secrecy (PFS) ensure in TLS?

Accepted Answer

Past session keys remain secure even if the long-term private key is compromised

Answer

All traffic is encrypted with a single master key

Answer

Session keys are never rotated

Answer

Certificates are always pinned

Question 5

Which mode of AES operation produces ciphertext blocks that are independent of each other, making it susceptible to block-swapping attacks?

Accepted Answer

ECB (Electronic Codebook)

Answer

CBC (Cipher Block Chaining)

Answer

GCM (Galois/Counter Mode)

Answer

CTR (Counter Mode)

Question 6

What is a Certificate Revocation List (CRL) used for?

Accepted Answer

Listing certificates that have been invalidated before their expiry

Answer

Listing all valid certificates in a PKI

Answer

Encrypting certificate data at rest

Answer

Binding domain names to IP addresses