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Jak odesílat zprávy, když někdo vypne Internet - Pavel Táborský

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Jak odesílat zprávy, když někdo vypne Internet - Pavel Táborský

  1. 1. How to get the message out, when “someone” shuts down the internet Pavel Táborský
  2. 2. Credentials • ~10+ years in IT, GSM networks before that • HAM License ~1 year • And that’s about it…
  3. 3. Credits... • Bruce Sutherland, KO4IN • How To Get Your Message Out When Your Government Turns Off The Internet – @DEFCON19
  4. 4. HAM Radio • Old tech since about 1900 • Usually two skilled operators needed, one at each end • Ionospheric conditions… • (Moon, Aircraft, Satellites)
  5. 5. Gear • Wet dream HF/SSB station – HF radio 40k+ – Mast + yagi dir antenna array ~100k – Power amplifier(s) etc. • Or on Budget: – Yaesu FT-897 ~20k – Longwire antena ~the cost of the wire – Essentially what WW2 operators did
  6. 6. We will use • HAM radio license… • APRS capable handheld radio ~5k • Yagi antenna made of tape measure and PVC pipe ~200 • VHF Band (145.825/144.800) • HAM radio satellite (OSCAR) – ISS – PC-SAT (Navy OSCAR – 44) • Twitter
  7. 7. We will use
  8. 8. Alternatively going cheap(er)
  9. 9. APRS • Developed in mid ‘80s by Bob Bruninga (WB4APR) • Originally position reporting system • Then Messages and WX reports • X.25 for HAMs – 1200baud – AFSK modulation • APRS is a retronym of WB4APR – Automatic Packet/Position Reporting System
  10. 10. APRS cont’d • The network consists of radio stations operating entirely with broadcasted packets • Digipeaters retransmit packets with store and forward approach and follow DIGIPATH • Packets are picked up by internet gateways (iGate) and handed over to the the APRS-IS to plot on a map • Allows for sending variety of packet types (position, object, telemetry, weather etc.)
  11. 11. APRS cont’d
  12. 12. Infrastructure needed • APRS iGate (preferably in another country) • APRS Digipeater (orbiting) • APRS -> Twitter gateway • Twitter
  13. 13. ISS Footprint
  14. 14. APRS via Satellite • Set radio transmit to 145.825 • ARISS on the 1st position in the digipath • Compose an APRS message to TWITR • Wait for the satellite to be over the horizon – And chosen iGate in the footprint • Send the message • Message gets digipeated back to ground iGate • And picked by the APRS-IS network • Subsequently by the APRS -> twitter gateway
  15. 15. APRS -> twitter gateway • Runs under hamradiotweets.com atm • Interfaces to the aprs.fi (APRS-IS) API to pull the messages • Tweets…
  16. 16. OSCAR • Stands for Orbital Satellite Carrying Amateur Radio • ISS • PC-SAT (Navy OSCAR-44) • OSCAR status: – http://oscar.dcarr.org/
  17. 17. Satellite pass prediction • Web Based – http://www.heavens-above.com/ – http://www.n2yo.com/ • Offline – Satscape
  18. 18. Not foolproof • The system can be jammed • You can be triangulated • Twitter fail whale

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