Week 1: Security Rules

Question 1

What is a bit?

Answer 1

Basic bit of information: 0 or 1

Question 2

What is a nibble?

Answer 2

Half a byte (4 bits)

Question 3

What is a hexadecimal value?

Answer 3

base 16 value (0-9, A-F)

Question 4

What are the 7 layers of the OSI model?

Answer 4

Layer 1: Physical Layer
Layer 2: Data Link Layer
Layer 3: Network Layer
Layer 4: Transport Layer
Layer 5: Session Layer
Layer 6: Presentation Layer
Layer 7: Application Layer

Question 5

OSI: What is the Physical Layer?

Answer 5

• 1st and lowest layer
• transmits raw bits
• converts electrical bits to electrical, radio or optical signals
• ie. wiring

Question 6

OSI: What is the Data Link Layer?

Answer 6

• 2nd layer
• node to node data transfer
• everything with MAC address
• ie. switch

Question 7

OSI: What is the Network Layer?

Answer 7

• 3rd layer
• routes data packets
• everything with router and IP address
• ie. router, TCP

Question 8

OSI: What is the Transport Layer?

Answer 8

• 4th layer

- how much information is communicated

Question 9

OSI: What is the Application Layer?

Answer 9

• 7th and most top layer
• application being used to send/receive information
• ie. browser

Question 10

OSI: What is the Presentation Layer?

Answer 10

• 6th layer

- ie. Operating system with firewall

Question 11

OSI: What is the Session Layer?

Answer 11

• 5th layer

- creates session between your computer and another computer/server

Question 12

What are the two security rules?

Answer 12

1. Don’t roll your own.

2. Kerckhoff’s Principle - secrecy of message should not depend on secrecy of algorithm

Question 13

How does the Caesar Cipher work?

Answer 13

Gen() - number key
Enc() - shift all letters forward by number key
Dec() - shift all letters backward by number key

Question 14

How does the Vigenere Cipher work?

Answer 14

Gen() - word key
Enc() - write out repeated word key underneath message and combine char values to create cipher text
Dec() - subtract word key repeatedly from ciphertext