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wireless-networks-overview.md

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Wireless networks overview

  • Wireless network = Wi-Fi
  • Type of Wireless Local Area Network (WLAN)
  • Standardized by IEEE 802.11
  • Allows devices in range of an access point to access the network.

Wireless terms

  • Access Point
    • Access Point (AP) or Wireless Access Point (WAP)
    • Hardware device that allows wireless connectivity to the end devices.
  • SSID (Service Set Identifier)
    • Unique name for a wireless Access Point
    • Inserted into the header of every data packet.
  • BSSID (Basic Service Set Identifier)
    • MAC address of an access point
  • GSM
    • Global System for Mobile Communication
  • Bandwidth
    • Amount of information that may be broadcasted over a connection
  • Hotspot
    • Places where wireless network is available for public use
  • Orthogonal Frequency Division Multiplexing
    • Encoding method of digital data on multiple carrier frequencies
  • Frequency-hopping spread spectrum (FHSS)
    • Method of transmitting radio signals rapidly switching a carrier among many frequency channels
  • Phase Shift Keying (PSK)
    • Modulation technique where phase of carrier signal changed by varying the sine and cosine inputs.
    • Widely used for WLANs, biometric and contactless operations, along with RFID and Bluetooth communications.

Antenna patterns

  • Antenna patterns - Polar coordinate system
  • 📝 Directional antenna patterns
    • Directional antenna
      • Also known as unidirectional antenna
      • Broadcasts and obtains radio waves from a single direction (can be e.g. 30 - 60 degrees)
      • E.g. Yagi (also known as Yagi–Uda antenna)
      • Most concentrated, higher range
      • Parabolic grid antenna
        • Based on the idea of a satellite dish
        • Can be attacked from farther away as it picks up Wi-Fi signal from 16 km and more
    • Bi-directional antenna
    • Omni-directional antenna
      • Broadcasts in 360 degrees
      • Most common type of antenna used in wireless communications and networks, especially WiFi
      • Used also in wireless base stations
      • Least concentrated and lower range
      • 3D illustration of omni-directional antenna
      • Dipole: Used for closer proximity e.g. mobile phones, client connections instead of site-to-site

Wireless encryption

Wireless encryption comparisons

WEP

  • Wired Equivalent Privacy
  • 1997, to provide data confidentiality
  • Stream cipher RC4 for confidentiality
  • CRC-32 checksum for integrity
  • Authentication using WEP-Open and WEP-Shared (using a shared key) modes
  • ❗ Weak as it reuses small IVs which allows decoding of its shared key.

WPA

  • Wi-Fi Protected Access
  • 2003, replace WEPs weak encryption
  • Uses Temporal Key Integrity Protocol (TKIP)
    • Major improvement over WEP
    • Dynamically changes key as system is used
    • Combined with larger IV, this defeats well known attacks
    • Uses RC4 encryption
  • Authentication using WPA-PSK and WPA-Enterprise modes
    • WPA-PSK uses pre-shared (symmetric) key to encrypt the wireless data
  • Improved payload integrity vs. WEP
    • Uses more secure message integrity check (MIC) known as Michael
    • Includes a frame counter to prevent replay attacks
  • Still subject to attack

WPA2

  • Also known as Wi-Fi Protected Access 2 or 802.11i
  • 2004, replace WPAs weak cipher
  • Authentication WPA2-Personal and WPA2-Enterprise modes
  • Uses Advanced Encryption Standard algorithm (AES)
    • Much harder to decrypt than WPA or WEP
  • 📝 Replaces TKIP with CCMP (AES-CCMP)
    • Also known as Counter Mode Cipher Block Chaining Message Authentication Code Protocol (Counter Mode CBC-MAC Protocol) or CCM mode Protocol (CCMP)
    • Uses AES as encryption algorithm instead of RC4 in WPA.

WPA3

  • Wi-Fi Protected Access 3
  • 2018, introduce Dragonfly handshake, protects against dictionary attacks
  • Authentication using WPA3-Personal and WPA3-Enterprise

Wireless cryptographic differences

WEP WPA WPA2 WPA3
Encryption RC4 RC4 + TKIP AES-CCMP AES-CCMP & AES-GCMP
IV Size (Bits) 24 48 48 48
Key Length (Bits)  40/140 128 128 128/256
Integrity Check CRC-32 Michael/CRC-32 CBC-MAC, CCMP BIP-GMAC-256

WPA2 and WPA3 Operation Modes

Personal
  • Intended for home use, easier setup
Enterprise
WPA2 vs WPA3 operation modes
Personal Enterprise
WPA2 Also called WPA-PSK (pre-shared key) as it uses PSK to protect network access Same encryption
WPA3 Also called WPA3-SAE (Simultaneous Authentication of Equals). Uses 128-bit key and Forward Secrecy against dictionary attacks. Uses 192-bit key

Wireless standards

  • 802.15.1 - Bluetooth

  • 802.15.4 - Zigbee

    • Low-power, low-data-rate, and close-proximity wireless ad hoc networks.
    • Popular IoT connection protocol

  • 802.16 - WiMAX

    • Wireless on "steroids"
    • Written for global development of broadband wireless metropolitan area networks.
    • Big range and fast.

  • Comparing wireless standards

  • 802.11 Specifications

    | Standard | Distance | Speed | | -------- | ----- | ----- | | WiFi | Medium (20-250 m) | Started slow (2 Mbit/s) but fast now (1300 Mbit/s) | | ZigBee | Smallest (1-100 m) | Slow (up to 0.25 Mbit/s) | | WiMax | Biggest (1.6 - 9.6 km) | Fast (up to 1 Gbit/s) |

  • 📝 Summary of the standards

    Standard Year Summary
    802.11 (WLAN/Wi-Fi) 1997 • 2.4 GHz • DSS, FHSS • Up to 2 Mbit/s • 20 - 100 meters
    802.11a (Wi-Fi 2) 1999 • 5 - 3.7 GHz • OFDM • Up to 54 Mbit/s • 35 - 100 meters
    802.11b 1999 • 5.4 GHz • DSSS • Up to 11 Mbit/s • 35 - 140 meters
    802.11c 2001  Bridge operation procedures; included in the IEEE 802.1D standard
    802.11d 2001 International (country-to-country) roaming extensions
    802.11e 2005 Enhancements: QoS, including packet bursting
    802.11f 2003  Inter-Access Point Protocol, Withdrawn February 2006
    802.11g (Wi-Fi 3) 2003 • 2.4 GHz • OFDM • Up to 54 Mbit/s • 38 - 140 meters
    802.11i 2004 Defines WPA/WPA2 encryption standards
    802.11n (Wi-Fi 4) 2009 • 2.4 - 5 GHz • MIMO-OFDM • Up to 600 Mbit/s • 70 - 250 meters
    802.11ac (Wi-Fi 5) 2012 • 5 GHz • MU-MIMO, • Up to 1300 Mbit/s • 70 - 250 meters
    802.11ax (Wi-Fi 6) 2019 • 1 - 6 GHz • MU-MIMO, OFDMA • Up to 11 Gbit/s • 70 - 250 meters
    802.15.1 (WPAN/Bluetooth) 2002 • 2.4 GHz • GFSK, π/4-DPSK, 8DPSK • Up to 50 Mbit/s • 70 - 250 meters
    802.15.4 (Low rate WPAN/ZigBee) 2003 • 0.868, 0.915, 2.4 GHz • O-QPSK, GFSK, BPSK • Up to 0.25 Mbit/s • 70 - 250 meters
    802.16 (WiMAX) 2005 • 2-11 GHz • SOFDMA • Up to 1 Gbit/s • 1.6 - 9.6 kilometers

  • See also all 802.11 standards and amendments

Wi-Fi authentication

Wireless authentication modes

Open system authentication process (OSA)

  • Uses WPA protocol.
  • Complete free for all, no auth at all
  • OSA - Open system authentication process sequence

Shared key authentication process (SKA)

  • Uses WEP protocol + a shared secret key
  • SKA - Shared key authentication process

IEEE 802.1x

  • 📝 Authentication mechanism for both wireless and physical access to a network
  • Authenticate devices to decide to give e.g. corporate or guest access
  • Switches uses back-end authentication server, see AAA
  • Can authenticate based on MAC address or other requirements (certificate, VLAN etc.)
  • Per default all hosts on a wired connection (LAN) can see each other