Re:Decoding the MetroCard, Part 2: Research and Past Attempts
by throwanem on Monday July 18, 2016 @06:30PM
(#12118407)
If your turnstiles can't talk to a server, they can't check key revocation lists, and I tend to imagine that in a city the size of New York somebody's going to leak a key every now and again - it's been known to happen with physical keys; why not digital ones, too?
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Re:Decoding the MetroCard, Part 2: Research and Past Attempts
by dsr_ on Monday July 18, 2016 @07:24PM
(#12118576)
But they don't need to have a realtime revocation list -- it's fine if a broken card works until the end of the day, or even the end of the week, as long as it stops working faster than keys are leaked or cracked.
So a bus turnstile can do transactions when it returns to the garage, and turnstiles in locations where it's hard to run data for whatever reason can get a plug-in every so often on a regular maintenance run.