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Lesson 3 The Media: Conducted and Wireless Roger Clery Roosevelt University cc Clery 2007

2. . . IntroductionThe world of computer networks and data communications would not exist if there were no medium by which to transfer data.The two major categories of media include: Conducted media Wireless media. 3. Transmission Media. All computer communication involves encoding data in a form of energy and sending the energy across a transmission medium.Electric current on wireRadio waves on air.

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Lesson 3 The Media: Conducted and Wireless Roger Clery Roosevelt University cc Clery 2007

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    1. 1 Lesson 3 The Media: Conducted and Wireless Roger Clery Roosevelt University (cc) Clery 2007

    2. 2

    3. 3 Transmission Media All computer communication involves encoding data in a form of energy and sending the energy across a transmission medium. Electric current on wire Radio waves on air

    4. 4 Wire

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    9. 9 Transmission Media Copper Wires Widely used because of low resistance to electric current, inexpensive and easy to install Three basic types: Unshielded Twisted Pair (UTP) Coaxial Cable Shielded Twisted Pair (STP)

    10. 10 UTP Media Unshielded Twisted Pair (UTP) wires Two insulated copper wires twisted together to reduce interference. Examples: Telephone wiring (one pair).LAN wiring UTP cable (4 pairs of copper wire)

    11. 11 STP Media Shielded Twisted Pair (STP) wires A metal shield surrounds the twisted pair wires that provides protection against interference STP wires are used in networks when cables pass by equipments that generate strong electromagnetic field (i.e. airconditioners)

    12. 12 Coax Media Coaxial cables Single wire surrounded by an insulation and a metal shield against interference. Example use: Cable TV wiring and early LAN wirings

    13. 13 Coax Layers

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    18. 18 Light

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    22. 22 Optical Fiber Media Media Four advantages over copper: Neither causes nor susceptible to electrical interference Can carry pulse much farther than copper Light can encode more information than electric One single fiber is sufficient to carry lots of data Disadvantages of optical fibers Installation requires special equipment If breaks it is difficult to find the location Special equipment is needed to repair a broken fiber. One single fiber is sufficient to carry lots of data so that if it is broken the outage is bigger

    23. 23 Fiber Optic Types multimode step-index fiber the reflective walls of the fiber move the light pulses to the receiver multimode graded-index fiber acts to refract the light toward the center of the fiber by variations in the density single mode fiber the light is guided down the center of an extremely narrow core

    24. 24 Fiber Optic Signals

    25. 25 Fiber Optic Advantages greater capacity (bandwidth of up to 2 Gbps) smaller size and lighter weight lower attenuation immunity to environmental interference highly secure due to tap difficulty and lack of signal radiation

    26. 26 Fiber Optic Disadvantages expensive over short distance requires highly skilled installers adding additional nodes is difficult

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    30. 30 Wireless (Unguided Media) Transmission transmission and reception are achieved by means of an antenna directional transmitting antenna puts out focused beam transmitter and receiver must be aligned omnidirectional signal spreads out in all directions can be received by many antennas

    31. 31 The Electro-magnetic Spectrum

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    36. 36 Satellite

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    43. 43 Satellite Transmission Applications television distribution a network provides programming from a central location direct broadcast satellite (DBS) long-distance telephone transmission high-usage international trunks private business networks

    44. 44 Principal Satellite Transmission Bands C band: 4(downlink) - 6(uplink) GHz the first to be designated Ku band: 12(downlink) -14(uplink) GHz rain interference is the major problem Ka band: 19(downlink) - 29(uplink) GHz equipment needed to use the band is still very expensive

    45. 45 Satellite Advantages can reach a large geographical area high bandwidth cheaper over long distances

    46. 46 Satellite Disadvantages high initial cost susceptible to noise and interference propagation delay

    47. 47 satellite

    48. 48 Radio

    49. 49 Common Carriers a government-regulated private company involved in the sale of infrastructure services in transportation and communications required to serve all clients indiscriminately services and prices from common carriers are described in tariffs

    50. 50 Radio before Cellular Fire, Police, Taxi radio services Semi-Duplex One freq for Base to Mobile Different Frequency for Mobile to Base First Cop radio 1620 KHz and 33MHZ

    51. 51

    52. 52 Evolution of Wireless Phones

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    60. 60

    61. 61 Cordless Phones

    62. 62 Wireless LANs

    63. 63 Basic Technology Concepts WiFi b-a-g

    64. 64 Basic Technology Concepts WiFi b-a-g

    65. 65 Bluetooth

    66. 66 Movies – You go online at home, see which movies are playing, order tickets, download them to home computer, do a wireless transfer over to PDA. Take PDA with you to movies. PDA communicates with ticket booth at movie theatre, you just walk right in. Or you walk up to your front door and your PDA communicates with your house – unlocks door, turns on lights, sets the heat/cool temperature, turns on the TV, etc. Other examples?Movies – You go online at home, see which movies are playing, order tickets, download them to home computer, do a wireless transfer over to PDA. Take PDA with you to movies. PDA communicates with ticket booth at movie theatre, you just walk right in. Or you walk up to your front door and your PDA communicates with your house – unlocks door, turns on lights, sets the heat/cool temperature, turns on the TV, etc. Other examples?

    67. 67 Channels and Media

    68. 68 Channels and Media

    69. 69 A Variety of Services

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    71. 71

    72. 72 Alternatives HTML –Lite No need to completely re-write WEB pages

    73. 73

    74. 74 Bypass

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    76. 76

    77. 77 Movies – You go online at home, see which movies are playing, order tickets, download them to home computer, do a wireless transfer over to PDA. Take PDA with you to movies. PDA communicates with ticket booth at movie theatre, you just walk right in. Or you walk up to your front door and your PDA communicates with your house – unlocks door, turns on lights, sets the heat/cool temperature, turns on the TV, etc. Other examples?Movies – You go online at home, see which movies are playing, order tickets, download them to home computer, do a wireless transfer over to PDA. Take PDA with you to movies. PDA communicates with ticket booth at movie theatre, you just walk right in. Or you walk up to your front door and your PDA communicates with your house – unlocks door, turns on lights, sets the heat/cool temperature, turns on the TV, etc. Other examples?

    78. 78 Sources of Wireless Errors Attenuation loss of electromagnetic energy Front end overload transmitter’s overwhelming filters in the receiver Narrowband interference overlapping of a small frequency band Spread spectrum interference frequency hopping or Direct Sequence Spread Spectrum (DSSS) Natural background noise Multipath interference interference due to multiple paths b/w the transmitter and the receiver

    79. 79 RFID A “new” kind of short range Data communication

    80. 80 What is RFID? Radio Frequency Identification: Identify physical objects through a radio interface. Many different technologies called “RFID”. Others types of non-radio auto-ID systems include: Optical barcodes Radiological tracers Chemical taggants

    81. 81 RFID System Primer Three Main Components: Tags, or transponders, affixed to objects and carry identifying data. Readers, or transceivers, read or write tag data and interface with back-end databases. Back-end databases correlate data stored on tags with physical objects.

    82. 82 RFID Adhesive Labels RFID Adhesive LabelsRFID Adhesive Labels

    83. 83 An RFID “Smart Shelf” Reader

    84. 84 System Interface

    85. 85 RFID History Earliest Patent: John Logie Baird (1926) “Identify Friend or Foe” (IFF) systems developed by the British RAF to identify friendly aircraft. Both sides secretly tracked their enemy’s IFF. How do you identify yourself only to your friends?

    86. 86 Digression #1: Related Military Applications IFF still used today for aircraft and missiles. Obviously classified. Could envision an IFF system for soldiers. Lots of military interest in pervasive networks of cheap, RFID-like sensors. Monitoring pipelines, detecting biological agents, tracking munitions, etc.

    87. 87 Commercial Applications Early Applications: Tracking boxcars and shipping containers. Cows: RFID ear tags. Bulky, rugged, and expensive devices. The RFID Killer Application?

    88. 88 Supply-Chain Management (Not Gum) First Universal Product Code scanned was on a pack of Juicy Fruit gum in 1976. Every day, over five billion barcodes are scanned around the world. But barcodes are slow, need line of sight, physical alignment, and take up packaging “real estate”. Over one billion RFID tags on the market. Example: Gillette’s “shrinkage” problem.

    89. 89 Modern RFID Applications Supply-Chain Management Inventory Control Logistics Retail Check-Out Access Control: MIT Proximity Cards. Payment Systems: Mobil SpeedPass. Medical Records: Pet tracking chips.

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    92. 92 Tag Power Source Passive: All power comes from a reader’s interrogation signal. Tag’s are inactive unless a reader activates them. Passive powering is the cheapest, but shortest range. Semi-Passive: Tags have an on-board power source (battery). Cannot initiate communications, but can be sensors. Longer read range, more cost for battery. Active: On-board power and can initiate communications.

    93. 93 Functionality Classes

    94. 94 Operating Frequencies

    95. 95 Asymmetric Channels Asymmetry result of passive tag vs. battery tag.Asymmetry result of passive tag vs. battery tag.

    96. 96 Security Risks: Espionage Corporate Espionage: Identify Valuable Items to Steal Monitor Changes in Inventory Personal Privacy Leaking of personal information (prescriptions, brand of underwear, etc.). Location privacy: Tracking the physical location of individuals by their RFID tags.

    97. 97 Espionage Case Study The US Food and Drug Administration (FDA) recently recommended tagging prescription drugs with RFID “pedigrees”. Problems: “I’m Oxycontin. Steal me.” “Bob’s Viagra sales are really up this month.” “Hi. I’m Alice’s anti-fungal cream.”

    98. 98 Security Risks: Forgery RFID casino chips, Mobil SpeedPass, EZ-Pass, FasTrak, prox cards, €500 banknotes, designer clothing. Skimming: Read your tag, make my own. Swapping: Replace real tags with decoys. Producing a basic RFID device is simple. A hobbyist could probably spoof most RFID devices in a weekend for under $50.

    99. 99 Security Risks: Forgery Mandel, Roach, and Winstein @ MIT Took a “couple weeks” and $30 to figure out how produce a proximity card emulator. Can produce fake cards for a few dollars. Can copy arbitrary data, including TechCash. Could read cards from several feet. (My card won’t open the door past a few inches.) Broke Indala's FlexSecur “data encryption”. (Just addition and bit shuffling. Doh.)

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    101. 101 Security Risks: Sabotage If we can’t eavesdrop or forge valid tags, can simply attack the RFID infrastructure. Wiping out inventory data. Vandalization. Interrupting supply chains. Seeding fake tags – difficult to remove.

    102. 102 Adversarial Model Can classify adversaries by their access. Three levels of read or write access: Physical: Direct access to physical bits. Logical: Send or receive coherent messages. Signal: Detect traffic or broadcast noise. Can further break down into Forward-only or Backward-only access.

    103. 103 Adversarial Model: Attacks Long-Range Passive Eavesdropper: Forward-Only Logical Read Access. No Write Access. Tag Manufacture/Cloning: No Read Access/Physical Read Access. Physical Write Access. Traffic Analysis: Signal Read Access. Jamming: Signal Write Access.

    104. 104 Adversarial Model: Countermeasures Countermeasures will degrade an adversary’s access. For example: Encryption degrades logical read access to signal read access. Authentication degrades logical write to signal write access. Tamper resistance can degrade physical read to logical read access.

    105. 105 Is it really that bad? Maybe Not. Tags can only be read from a few meters.* Will mostly be used in closed systems like warehouses or shipping terminals. Can already track many consumer purchases through credit cards. Difficult to read some tags near liquids or metals. Can already track people by cell phones, wireless MAC addresses, CCTV cameras, etc.

    106. 106 But…the customer is always right. The public perception of a security risk, whether valid or not, could limit adoption and success. Similar to Pentium III’s unique ID numbers. Successful boycott of Benetton. Privacy advocates have latched on: “…e-mails sent to the RFID Journal…hint at some of the concerns. ‘I'll grow a beard and f--k Gillette,’ wrote one reader”, Economist Magazine, June 2003. “Auto-ID: The worst thing that ever happened to consumer privacy”, CASPIAN website.

    107. 107 Security Challenge Resources, resources, resources. EPC tags ~ 5 cents. 1000 gates ~ 1 cent. Main security challenges come from resource constraints. Gate count, memory, storage, power, time, bandwidth, performance, die space, and physical size are all tightly constrained. Pervasiveness also makes security hard.

    108. 108 Example Tag Specification

    109. 109 Resource Constraints With these constraints, modular math based public-key algorithms like RSA or ElGamal are much too expensive. Alternative public-key cryptosystems like ECC, NTRU, or XTR are too expensive. Symmetric encryption is also too costly. We can’t fit DES, AES, or SHA-1 in 2000 gates. (Recent progress made with AES.)

    110. 110 Simson’s Bill of Rights The RFID Bill of Rights: The right to know whether products contain RFID tags. The right to have RFID tags removed or deactivated when they purchase products. The right to use RFID-enabled services without RFID tags. The right to access an RFID tag’s stored data. The right to know when, where and why the tags are being read.

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    118. 118 End of Chapter III

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