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How they know where you are. GEO PRIV @IETF88. GPS. Privacy/Surveillance : OK Performance: Um…. 1500 bits@50bps = too damned long. A-GPS. Terrestrial networks are waaaay faster Send ephemeris that way. A-GPS Modes. Device-based “I am here, send me ephemerides”

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How they know where you are


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Presentation Transcript
slide2
GPS

Privacy/Surveillance: OK

Performance: Um…

1500 bits@50bps= too damned long

a gps
A-GPS

Terrestrial networks are waaaayfaster

Send ephemeris that way

a gps modes
A-GPS Modes
  • Device-based
    • “I am here, send me ephemerides”
    • Often tied to another location technology
      • Cell-based positioning is often performed by the server
      • A very coarse seed is often sufficient
    • Device performs final calculation
  • Device-assisted
    • “Duh…”
    • Can use arbitrarily-accurate location
      • Fast methods are preferred
    • Server tells Device where to look for signals
    • Device just looks for signals and reports code phases
    • Server performs final calculation
control vs user plane
Control vs. User Plane
  • Initial A-GPS deployments used the cellular control channels: SLOW
  • Secure User Plane Location replaces that
    • Operates over the Internet
    • “Secure” because it’s TLS
    • Inherits most of the architectural characteristics
      • Server command and control
      • Roaming arrangementsand policy enforcement models
      • Application requests a core part
realities of supl deployment
Realities of SUPL Deployment
  • A few very large providers
    • Cellular carriers and mobile OS vendors
  • All of these have your location
    • Even in Device-initiated, Device-based A-GPS, the server tends to get a copy of the result
  • SUPL is typically baked into silicon and not visible to the mobile OS
    • Most people don’t even know how to access config

“Go to the phone’s dialer and enter the number ##1472365##“

  • Disabling the GPS is for most, the only option
a solution
A Solution
  • Make assistance data free
    • GPS does anyway
    • Just make it available faster
  • No strings attached
    • Don’t request location-specific assistance
  • …but
    • This field is IPR-rich and many have staked a claim
    • No strong incentive to give assistance data away
    • Invalidates some location integrity options
other location technologies in active wide deployment
Other Location Technologies in Active, Wide Deployment
  • WiFi access point databases
    • Servers almost mandatory due to volume of data
    • Servers use GPS results to improve their datasets
  • Cell-based and enhanced cell-based
    • Based on existing network/radio management data
    • Some use Device-reported measurements
  • OTDOA and UTDOA
    • Based on observed time difference of arrival at Device or cell towers respectively
    • OTDOA uses Device measurements; again probably invisible
    • UTDOA is measured in the network; can be done without Device being aware that it is happening; kinda pricey though