[PLUG-TALK] TriMet HOP card teardown

Keith Lofstrom keithl at kl-ic.com
Thu May 23 21:02:43 UTC 2019


Do any of you know of a published microscopic teardown
of the chip attached to the RFID tag embedded in the
TriMet "HOP" card?  The manufacturer is EDM, Electronic
Data Magnetics.

I scrubbed the paper off the plastic inner card to reveal
a seven-loop near-field RF coil.  My guess is 13.56 MHz,
a few microwatts.  That is vastly less dangerous than the
up-to-one-watt cell phone you hold next to your brain.
That's not my worry.

The chip is approximately 0.7 mm square; that's gynormous,
and could hold kilobytes of memory with a modern "cheap"
chip process (with 1% of the density of Intel's 14
nanometer marvels).

I no longer own the lab tools to tear down chips, but some
universities do.  Perhaps someone reading this can tell us
more about this chip.

----

I presume the card is merely an ID token, and that the HOP
reader transmits the ID data to TriMet's database.  While
I assume they track us to maximize transit connectivity
and efficiency, I doubt they can stop other organizations
(domestic and foreign) from harvesting that data.

I realize most people believe "privacy is dead", and accept
information asymmetry and personal powerlessness as the
"new normal".  My genome suggests an ancestor or two who
escaped slavery, so my genes beg to differ.

To TriMet we may be "data products", but I hope we (the
thoughtful geeks) can learn enough to tilt the balance
a little more in the direction of individual citizen
empowerment.  That begins with watching the watchers.

Questions: Which neighborhoods feed the most transit users
to a specific political rally?  How are federal funds 
apportioned between neighborhoods?  Are these related?

Keith

-- 
Keith Lofstrom          keithl at keithl.com



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