Wireless Security

Question 1

Wireless Security methodologies and design factors

Answer 1

• Channel characteristics
• Authentication
• Authorization
• Encryption
• Latency
• Complexity
• Intercept probability
• Secrecy capacity (communication rate of secret information)

Question 2

What is modulation?

Answer 2

Describes changes applied to a carrier signal by a modulating signal
-> changes amplitude, frequency, or offset/phase

Question 3

Amplitude Shift Keying

Answer 3

• Modifies the amplitude of the carrier signal
• Amplitude can be modified from zero to max or by using an offset from zero to not confuse silence with a symbol.

Question 4

Frequency Shift Keying

Answer 4

In frequency shift keying each symbol is defined by a different frequency

Question 5

Phase Shift Keying

Answer 5

In phase shift keying each symbol is defined by a different phase offset

Question 6

Digital quadrature amplitude modulation

Answer 6

• The combination of amplitude shift keying and phase shift keying is called quadrature amplitude modulation
• Makes it possible to encode more information (bits) into a single symbol

Question 7

Different types of jammers

Answer 7

• Constant jammer
• Intermittent jammer
• Reactive jammer (only if transmission is detected)
• Adaptive jammer (tailored to the level of received power at the legitimate receiver)
• Intelligent jammer (exploit weaknesses of the upper-layer protocols)

Question 8

Prevention of jamming

Answer 8

• Channel hopping
  -> Change the frequency using an unpredictable sequence (for the attacker)
  -> Jamming the whole bandwidth consumes too much power
• Spread spectrum: Use a wider spectrum to spread the transmission instead of using a single frequency
• Beam forming
  -> Use multiple antennas for communication and “aligned” to the communication partner
  -> An attacker cannot jam all antennas equally

Question 9

Main types of signals

Answer 9

• Electric current
  -> wired connections, e.g., Ethernet
• Electromagnetic waves
  -> Wireless connection through air, e.g., WLAN
  -> Transmitting data using light, e.g., fibre connections
• Acoustic waves
  -> Wireless connection through mediums where electromagnetic waves do not propagate well, e.g., underwater sonar systems of submarines

Question 10

Amplitude

Answer 10

• Maximum displacement from 0
• Strength of a signal
• Declines with increasing distance

Question 11

Magnitude

Answer 11

• Size of an entity compared to other entities
• In the frequency domain for signals: Strength of a signal at a certain frequency in comparison to signals at other frequencies

Question 12

Frequency

Answer 12

1 Hertz = 1 sine wave per second

Question 13

Phase

Answer 13

Offset from the normal sine wave starting point

Question 14

Digital Modulation

Answer 14

Digital signals are applied to a carrier signal (called switching or keying)
-> Each bit gets converted to a symbol representing that bit. A symbol is a specific value lasting a specified time to represent.

Question 15

Main attack vectors on wireless physical layers

Answer 15

• Eavesdropping
  -> WPA3, VPN
• Injection
• Jamming