Encryption for Security

Question 1

What is Secret-Key Encryption?

Answer 1

Uses one shared key for both encryption & decryption.

Main challenge = secure key exchange. Common ciphers: DES, RC4, AES, Blowfish, Twofish, IDEA.

Question 2

What is the difference between Block and Stream Ciphers?

Answer 2

Block: Encrypts chunks (e.g. 128-bit blocks).
Stream: Encrypts bit-by-bit in real-time.

Use stream for speed & low latency (e.g., voice, video).

Question 3

What are common types of Hash Attacks?

Answer 3

Rainbow Table: Precomputed hashes used to reverse plaintext.
Brute-Force: Try all possible combinations.
Dictionary: Try common words.
MITM: Intercept communication.

Question 4

What is Salting in encryption?

Answer 4

Salt: Random data added to make hashes unique.
Entropy: Unpredictability = stronger encryption.

Salting + strong entropy = better hash protection.

Question 5

What is the problem with Key Exchange?

Answer 5

Problem: How to safely share secret keys.
Perfect Forward Secrecy (PFS): Past keys stay secure if long-term key is leaked.

Methods: DHE / ECDHE (temporary, per-session keys), Public key exchange.

Question 6

What are the Key Exchange Quiz Tips?

Answer 6

PFS = Protects past session keys.
To share a key: Sender encrypts session key with receiver’s public key.

Question 7

What is Tunneling in data protection?

Answer 7

Used to protect data in untrusted networks.

Techniques: VPN, SSL/TLS, IKE (Internet Key Exchange), Tor (onion routing).

Question 8

What are the quick facts about SSL/TLS?

Answer 8

Tunnel built with symmetric keys.
Server sends: Digital certificate, Cipher suites.
Uses asymmetric encryption to exchange session key.

After handshake, communication is symmetric.