Bertels Wireless Networks.pptx

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Bertels Wireless Networks.pptx Powered By Docstoc

               Jacob Bertels
       Christopher Rawlings
 What is a Wireless Network?
 Basic network is WLAN- Wireless LAN
 Most based on the IEEE 802.11 standards
 Use IP and MAC address
 WPAN– Wireless Personal Area Network
 Bluetooth
 Infrared Data
  Association (IrDA)
 Near Field
More Wireless Networks
 WWAN- Wireless Wide Area Network
 Mobile Telecommunications cellular network
 LTE, Uses Encryption and Authentication
 Point-to-point and Omnidirectional
 Cellular Networks- Towers
 Different Frequencies
 Cell phones- Tower Handoff
 Signal-to-Noise
Wireless Mesh Networks

          Mesh Topography of Routers
          Usually Fixed mesh routers
           form a multi-hop structure of a
          Can be modeled as a graph
          Edge would be: Distance, Data
           Rate, Noise, Frequency
          Mesh is “self-healing”
      Mesh Network Cont.
 Load Balancing Priority over Shortest Path
 Measures current congestion on each path
 Continually runs algorithm
 Better Approach To Mobile Adhoc
  Networking (B.A.T.M.A.N.)
 Detects other nodes, informs neighbors
 Sends out , node remembers direction
 Cares only about the best first step
 Dynamically creates routes
   Data Packet Scheduling
 Minimize resource starvation and make fair
 Some Routers and switches use First-In-First
  -Out (FIFO)- Based in a Queue
 Round Robin
 Separate Queue for every data flow
 Algorithm lets each data flow to take turns
 Can use Weight Round Robin for Priorities
          Error Correction
 Forward Error Correction
 Encodes Redundancy for Verification at
 Simple FEC- (3,1) repetition code (inefficient)
 Repetition of same byte multiple times
 Parity Bits are used
 Sets the last bit (odd or
  even number of 1s)
 Hamming(7,4)
Error Correction Cont.
Multidimensional Parity-Check Code
Ex. Want to send: 2541
Split up into 25, 41, add parity
Goes to 257,415, add digits 66
Send code 25741566- Decoder receives
Error Correction Cont.
   Turbo Code- Used for 3G and Satellite
   Encoder- Takes input converts to three outputs
   Interleaver scrambles input into pseudo-random pattern
   Redundancy is added in each Encoder
   Multiple outputs ensures consistency
Error Correction Cont.
 Turbo Code- Decoder
 Decoder tries to decode each input
 Uses feedback and iteratively verifies
  data is correct
What is WEP?
 Wired Equivalent Privacy
 First Wifi encryption standard
 Uses stream cipher RC4
 Two Key sizes
   64bit
   128bit
How WEP Encryption Works
              Start with a Key
              Make a pseudo
               random Initialization
              Concatenate the Key
               with the Initialization
               Vector(IV) to make a
              The Keystream is then
               XOR’ed with the plain
               text dataEncrypted
Collecting Data
Generating Traffic
Collecting Data
Password Broken
What is WPA?
 Wi-Fi Protected Access
 Used as a time filler until WPA2 ratified
WPA Strengths
 Still used RC4 cipher, but increased the
  IV length to 48 bits
 Also used a different keystream for each
 Began salting the key with the network
   Causes computation time to increase
WPA Flaws
 Small packets such as ARP packets or
  DNS packets are crack-able
 Still very difficult because of key size
What is WPA2?
 Wi-Fi Protected Access II
   Also called Full IEEE 802.11i or IEEE
    ○ But who really wants to remember that
 Current top of the line wireless security
WPA2 Strengths
 Very Large Key
   256 bits
 Uses AES algorithm
   Not a stream Cipher
   Based on 4x4 Matrices
   Not going to go into much detail
    ○ Don’t want to steal another group’s topic too
WPA2 Weakness
 Only one major weakness
   Not even in the algorithms
 WPS Flaw
   Wi-Fi Protected Setup
   Allows easy secure network connectivity
   Has a pin made up of 8 numbers
    ○ Grouped in 2 groups 4&4
   If an attacker can break the pin, they can get
    the encryption key without breaking the
Breaking WPA
 Must capture “4 way handshake”
 Only real way is to brute force the
 You must have a list of “words” to try as
 Can have a list of words ready for
  attacking or have a program that makes
  the words on the fly
Capture 4 Way Handshake
Brute Forcing Password
Password Found
Breaking WPA
 You can pre-compute the hashes
   Rainbow tables(hash tables)
   ○ Contain the hash and the corresponding key
   ○ They still have to be computed, but they can
     be computer beforehand and kept
   ○ Church of Wifi rainbow tables ~45GB
      1000 top network names
      ~1,000,000 passwords
Breaking WPA
 Either way, if a complex password is
  used, breaking the password becomes
  mathematically impossible
Breaking WPA Example
 64 character password
 94 possible characters(full keyboard)
 Possible passwords=7.33x10^126
 @1googolplex(10^100/s)
 On average to brute force it would take

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