CP372 Networks Chapter 8 Questions

What is confidentiality in network security?

Ensures only the sender and intended receiver can understand the message.

What does authentication guarantee?

The communicating party is who they claim to be.

What is message integrity?

Assurance that a message has not been altered in transit.

What is a nonce and why is it used?

A random value used once to prevent replay attacks.

What is the key difference between symmetric and public-key cryptography?

Symmetric uses a shared key; public-key uses a public/private key pair.

What problem does public-key cryptography solve?

Secure key distribution between unknown parties.

What is a digital signature used for?

Authentication, integrity, and non-repudiation.

What is a message digest?

A fixed-length hash representing a message.

Why is AES preferred over DES?

AES uses longer keys and is resistant to brute-force attacks.

What is the goal of Diffie–Hellman?

To establish a shared secret without sending it directly.

TLS uses symmetric encryption for data transfer.

True - symmetric encryption is efficient for bulk data.

Encrypting a password alone prevents replay attacks.

False - freshness (e.g., nonce) is required.

RSA is efficient for encrypting large files.

False - it is slow and used mainly for key exchange.

Hash functions provide confidentiality.

False - they provide integrity, not secrecy.

ESP provides confidentiality while AH does not.

True.

Which attack involves resending a captured message?

A. Spoofing

B. Replay

C. Eavesdropping

D. Hijacking

Answer: B

Which key verifies a digital signature?

A. Sender’s private key

B. Receiver’s private key

C. Sender’s public key

D. Receiver’s public key

Answer: C

Which protocol secures TCP connections on the web?

A. IPsec

B. TLS

C. SSH

D. DNSSEC

Answer: B

Which IPsec mode encrypts the entire IP datagram?

A. Transport

B. Record

C. Tunnel

D. Session

Answer: C

Which firewall tracks active TCP connections?

A. Stateless

B. Packet filter

C. Application gateway

D. Stateful

Answer: D

Why are message digests signed instead of full messages?

They are smaller and faster while still ensuring integrity.

Why does TLS use multiple keys?

To separate encryption and authentication for better security.

Why is a CA needed?

To bind a public key to a real identity and prevent MITM attacks.

Why is 0-RTT TLS vulnerable to replay attacks?

Early data can be reused by attackers.

Why is IPsec connection-oriented?

It relies on stateful Security Associations (SAs).

An attacker reuses a captured login message. What attack? How to stop it?

Replay attack; prevent using nonces or sequence numbers.

Alice signs a message and Bob verifies it. What is guaranteed?

Authentication, integrity, and non-repudiation.

Why does TLS switch to symmetric encryption after handshake?

Symmetric encryption is faster for bulk data.

What IPsec field prevents replay attacks?

Sequence number.

Why can’t a stateless firewall detect fake TCP ACK packets?

It does not track connection state.