1. Introduction to Cyber Security

Question 1

common cyber security attackers

Answer 1

1. script kiddies
2. hackers (white, grey, black)
3. insiders
4. cyber criminal groups
5. hacktivist

Question 2

cyber crime motivations

Answer 2

1. bragging rights
2. money
3. steal, alter, delete information
4. revenge
5. state sponsored spying etc

Question 3

types of cryptography

Answer 3

1. symmetric key
   - encryption and decryption use the same key
   - private, only known to sender and receiver
2. asymmetric key
   - encryption and decryption use different key
   - public key for encryption
   - private key for decryption
3. hashing
   - no keys
   - one way functions to convert plain txt to fixed length hashed value

Question 4

symmetric cryptography

Answer 4

1. substitution cypher
   - mono alphabetic (Caesar cypher)
   - poly alphabetic (Vegenere cypher)
2. transposition cypher
   - simple transposition
   - rail fence cypher
   - columnar transposition

Question 5

vulnerabilities of symmetric cryptography

Answer 5

if algorithm is know, easy to decrypt

Question 6

how to solve vulnerabilities of symmetric cryptography

Answer 6

1. approach
   - DES
   - 3 DES
   - AES
2. approach
   - OTP

Question 7

asymmetric cryptography

Answer 7

keys are generated in pairs using one way function
choose one as public, one as private
public key to encrypt
private key to decrypt

Question 8

how to authenticate users using asymmetric keys

Answer 8

if use public key to encrypt, private key to decrypt –> confidentiality
if use public key to decrypt, private key to encrypt –> authentication

sender signs text with sender private key
sender encrypts signed text with receiver public key
receiver decrypts with receiver private key
receiver verify with sender public key

Question 9

key generation

Answer 9

1. modular arithmetic
2. prime factorisation
   - RSA key generation

Question 10

RSA key generation

Answer 10

1. pick 2 large prime P, Q
2. calculate n = PQ
3. calculate N = (P-1)(Q-1)
4. pick e = number < N, co prime to N
5. calculate d where d x e x mod(N) = 1
6. public key = (e, n)
7. private key = (d, n)

Question 11

deffie hellman key exchange

Answer 11

alice calculates: A = pow(G,a) x mod(P)
bob calculates: B = pow(G,b) x mod(P)

shared information: A, B, P, G

alice calculates: K = pow(B,a) x mod(P)
bob calculates: K = pow(A,b) x mod(P)

Question 12

what is the CIA triad

Answer 12

1. confidentiality
   - prevention of unauthorised disclosure of information
2. integrity
   - prevention of unauthorised modification of information
3. availability
   - prevention of unauthorised withholding of resources