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NYarvin's profile
Norman Yarvin
Norman Yarvin
Norman Yarvin
@NYarvin

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Norman Yarvin

@NYarvin

yarchive.net/blog
Joined April 2013

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    1. Matthew Green‏ @matthew_d_green 4 Dec 2016
      • Report Tweet
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      Replying to @matthew_d_green

      If they did, then the device is functioning exactly as designed. This is not a "break" or a "hack". 10/

      1 reply 5 retweets 20 likes
    2. Matthew Green‏ @matthew_d_green 4 Dec 2016
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      Replying to @matthew_d_green

      If you're judging implantable device security, the question you should ask is: can I send a shock command *from a distance*... 11/

      6 replies 11 retweets 27 likes
    3. Matthew Green‏ @matthew_d_green 4 Dec 2016
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      Replying to @matthew_d_green

      ... without first making close (<10cm) physical contact with the patient. If the answer is "no", then the device is working as intended. 12/

      4 replies 8 retweets 19 likes
    4. Matthew Green‏ @matthew_d_green 4 Dec 2016
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      Replying to @matthew_d_green

      And last point: "we think we could extend the range someday" is not an answer. It usually means the researchers don't understand RF. 13/

      3 replies 6 retweets 36 likes
    5. Matthew Green‏ @matthew_d_green 4 Dec 2016
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      Replying to @matthew_d_green

      In practice, most implantable devices use an inductive (EM) channel for initial contact. These have 1/R^3 signal strength dropoff. 14/

      4 replies 7 retweets 28 likes
    6. Matthew Green‏ @matthew_d_green 4 Dec 2016
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      Replying to @matthew_d_green

      Unlike ordinary RF which has 1/R^2 signal strength dropoff. Extending EM range is not as easy as just "build a slightly bigger antenna". 15/

      3 replies 10 retweets 29 likes
    7. Dan‏ @captain_test 4 Dec 2016
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      Replying to @matthew_d_green

      EM and RF are the same thing, I assume you mean a magnetic field?

      1 reply 0 retweets 1 like
    8. Matthew Green‏ @matthew_d_green 4 Dec 2016
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      Replying to @captain_test

      I mean inductive coupling. That's correct. Most manufacturers call it "EM" as opposed to "RF".

      1 reply 3 retweets 14 likes
    9. Norman Yarvin‏ @NYarvin 4 Dec 2016
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      Replying to @matthew_d_green

      Well, inductors do couple with radiation, as in a loop antenna or the common AM antenna.

      1 reply 0 retweets 0 likes
    10. Norman Yarvin‏ @NYarvin 4 Dec 2016
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      Replying to @NYarvin @matthew_d_green

      The trick that implantable devices use is to operate at low frequencies (less than a MHz), where transmission is hard.

      1 reply 0 retweets 3 likes
      Norman Yarvin‏ @NYarvin 4 Dec 2016
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      Replying to @NYarvin @matthew_d_green

      At low frequencies, unless you have a huge antenna you get a lot of near field without much far field.

      8:18 AM - 4 Dec 2016
      • 3 Likes
      • 🇭🇰 Peter Barfuss 𒀱 Rene Mayrhofer Matthew Green
      1 reply 0 retweets 3 likes
        1. New conversation
        2. Norman Yarvin‏ @NYarvin 4 Dec 2016
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          Replying to @NYarvin @matthew_d_green

          So your basic point is correct, but "near field" vs "far field" is the proper technical terminology, not RF vs inductive.

          3 replies 4 retweets 19 likes
        3. Matthew Green‏ @matthew_d_green 4 Dec 2016
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          Replying to @NYarvin

          Ha, I never said *I* understand RF either ;) But good to know I'm not fundamentally wrong.

          0 replies 0 retweets 6 likes
        4. End of conversation

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