Section 2: Cryptography

Question 1

What is obfuscation?

Answer 1

Hide something to make it confidential.

Question 2

Explain the Caesar Cipher

Answer 2

Substitute a letters

Question 3

What is ROT2?

Answer 3

Shifted the letters along 2 places.

A becomes C

Question 4

Vigenere Cypher

Answer 4

A key is used on the plain text and then matched against a caesar cypher table. Great for the alphabet.

Question 5

What are the 2 classic cryptography components?

Answer 5

1. Algorithm

2. Key for encryption

Question 6

XOR - Exclusive OR

Answer 6

Similar to vigenere but for binary

Question 7

What is Kerckhoffs’s principle?

Answer 7

Everybody knows the algorithm but the key is secure.

Question 8

What is data at rest?

Answer 8

Stored media

Question 9

What is data in transit?

Answer 9

Phone calls etc

Question 10

What is Data in Process?

Answer 10

Data in RAM, CPU

Question 11

How do you send an encryption key?

Answer 11

asymmetric encryption

Question 12

In-band v out-of-band

Answer 12

Sending the key with the encrypted data, vs physically taking.

Question 13

What is an Ephemeral Key?

Answer 13

Temporary Key - provides perfect forward secrecy.

Question 14

What is asymmetric encrption?

Answer 14

Uses a key pair - public + private.

Public used to encrypt
Private used to decrypt

Slow and onerous. Great for exchanging session keys.

Question 15

What is a Cryptosystem?

Answer 15

Sets the rules of the system - key properties - length. Communications requirements for key exchange and the actions for encryption and decryption.

Question 16

What is symmetric encrption?

Answer 16

Using the same key to encrypt and decrypt.

Question 17

What is DES

Answer 17

Data Encryption Standard - a symmetric block algorithm, invented by IBM. First open standard by gov.

Question 18

How does DES work?

Answer 18

64 block
Create a key and subkey
Perform Feistel Function
Expansion function
XOR
8 S Boxes
Final permutation

Question 19

What types of block encryption replaced DES?

Answer 19

Blowfish and Triple DES.

Question 20

What 3 things are important for a block cypher?

Answer 20

Key size
Number of rounds
Block size

Question 21

What are DES stats?

Answer 21

64-bit Block size
16 Rounds
56 bit Key Size

Question 22

What are Triple DES stats?

Answer 22

64-bit Block size
16 Rounds
x3 56 bit Key Size

Question 23

What are the Blowfish stats?

Answer 23

64-bit Block size
16 Rounds
32 - 448 bit Key Size

Question 24

What is the AES? When did it come out?

Answer 24

Advanced Encryption Standard released in early 2000s. Unhackable! Supported by the NIST.

Question 25

What are AES stats?

Answer 25

128-bit Block size
10, 12 or 14 Rounds
128, 192 or 256 bit Key Size

Question 26

What is a Streaming Cypher?

Answer 26

Each bit is encrypted one by one.

Question 27

What is RC4?

Answer 27

Rivest Cipher 4
Streaming Cypher
No Blocks, 1 Round, Key Size 40 to 2048-bits