Cyber Security Cryptography 2 — Questions and Answers
Question 1: What is PKI (Public Key Infrastructure) primarily responsible for?
- Managing firewall rules
- Issuing and managing digital certificates for trusted identities (Correct answer)
- Encrypting database records
- Scanning for vulnerabilities
Correct answer: Issuing and managing digital certificates for trusted identities
PKI manages the lifecycle of digital certificates, enabling trusted authentication and encryption across systems.
Question 2: Which key is used to encrypt a message so that only the intended recipient can decrypt it?
- The sender's private key
- The recipient's public key (Correct answer)
- A shared symmetric key
- The CA's root key
Correct answer: The recipient's public key
Encrypting with the recipient's public key ensures only the holder of the corresponding private key can decrypt it.
Question 3: What does salting a password hash protect against?
- Brute force via CPU speed
- Rainbow table and precomputed hash attacks (Correct answer)
- Man-in-the-middle attacks
- Session hijacking
Correct answer: Rainbow table and precomputed hash attacks
Adding a unique random salt before hashing prevents attackers from using precomputed rainbow tables.
Question 4: Which mode of AES operation turns the block cipher into a stream cipher by XORing plaintext with an encrypted counter?
- ECB
- CBC
- CTR (Correct answer)
- OFB
Correct answer: CTR
CTR (Counter) mode encrypts successive counter values and XORs the result with plaintext, enabling parallel processing.
Question 5: What is forward secrecy in TLS?
- Using the same key for all sessions for consistency
- Generating unique session keys so past sessions remain secure if long-term keys are compromised (Correct answer)
- Requiring client certificates in all TLS handshakes
- Encrypting the TLS handshake with a pre-shared key
Correct answer: Generating unique session keys so past sessions remain secure if long-term keys are compromised
Forward secrecy ensures that session keys are not derivable from long-term keys, protecting past communications.
Question 6: What type of attack attempts every possible key combination until the correct one is found?
- Dictionary attack
- Brute force attack (Correct answer)
- Side-channel attack
- Birthday attack
Correct answer: Brute force attack
A brute force attack systematically tries every possible key or password until the correct one is found.
Cyber Security Cryptography 2
What is PKI (Public Key Infrastructure) primarily responsible for?