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The tiny chip that powers Montreal subway tickets

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Re: The tiny chip that powers Montreal subway tickets

#71

Post by jcynix »

jeffbee wrote: post #6
kens wrote: post #2

Author here for all your NFC chip questions :-)

Is this the same system used by Boston MBTA? I was surprised to see single-use tap cards when I visited there for the first time yesterday. I wondered why the ticket isn't reloadable.

Single tap cards are usually just used with their "hardwired" chip serial number. That is stored in a central system which invalidates the number once you used it. This makes it rather easy (even if its environmentally unfriendly) to issue these cards: load a number of cards into your machine, register the serial number and invalidate it when used.

Re: The tiny chip that powers Montreal subway tickets

#72

Post by lxgr »

kens wrote: post #67
lxgr wrote: post #46

Earlier quoted context omitted.

Ultralight supports password authentication, and you can diversify the password from the serial number, meaning that until that password is revealed by a legitimate reader as part of a validation transaction (at which time the ticket is invalidated anyway), you can't clone it. Ultralight C does support actual cryptographic authentication.

I don't think the password authentication helps against cloning. You could start a transaction and stop after you get the password. Then you could clone the card. (The system could invalidate the ticket as soon as they get the UID, but that would be a reliability nightmare since a failure during the read would invalidate someone's ticket.)

You could do that, but it still greatly raises the cost for an attacker, since they need to hang around a ticket validator for every ticket they want to clone, as opposed to e.g. a QR code ticket, which can be trivially copied by a simple screenshot.

Also, many of these transit systems are eventually consistent (they're usually offline-capable for resilience, but usually manage to send all validation transactions to a backoffice system within at most a day, and often minutes).

This allows detecting duplicate usage fairly quickly. In systems where you need to tap out as well as tap in to leave the turnstile, that's where ticket inspectors might take a sudden interest in you if you tap out with a cloned ticket.

In the end, as with most security systems, the goal is not to make fraud absolutely impossible, but to make it economically non-viable.

Re: The tiny chip that powers Montreal subway tickets

#74

Post by scrollaway »

cypherpunks01 wrote: post #63

My favorite household NFC usage? NFC alarm clock. Makes me get out of bed and tap my phone on a specific NFC tag placed somewhere around the house, in order to turn off the alarm. Then, I may as well wake up, since I'm already out of bed : ) It's a nice companion to help perform 'habit stacking' as Atomic Habits calls it. Want to do pushups right after waking up? Place an NFC card under your workout mat, so you're fo…

> Makes me get out of bed and tap my phone on a specific NFC tag placed somewhere around the house, in order to turn off the alarm.

Neat, but is there an advantage between this and "Place the alarm clock further from the bed"?

Re: The tiny chip that powers Montreal subway tickets

#75

Post by dgudkov »

localfirst wrote: post #13

Comparing Montreal subway with Vancouver's skytrain: - Montreals subway stations have this gritty, distinctively french atmosphere i loved it. - Vancouvers above/below stations have no soul, distinctively anglo but above ground ones i liked. - Montreal train cars use rubber wheels to my shock! Extremely loud. - Vancouver train cars use some sort of electric system which im not familiar with ( have a few variants (new…

>Montreal subway does not cover the entire region like Vancouver's skytrain.

It's not supposed to. The new REM train network (a few stations already in use) will cover the region. By 2027. Maybe.

REM will also go to YUL.

PS. Fun fact, REM is also driver-less just like the Skytrain.

Re: The tiny chip that powers Montreal subway tickets

#76

Post by chx »

mschuster91 wrote: post #42

> The Ultralight chip has a few features beyond a printed ticket, though. The chips are manufactured with a unique 7-byte identification code (UID). Moreover, the UID is signed, ensuring that fake UIDs cannot be generated. The problem is, they can be just as easily cloned . Your average Flipper Zero can do that. If you want actual security, you have to go for a challenge-response scheme - i.e. every card is provision…

It's utterly not worth it. Your time to get it working, the equipment... but even if you have all of those if you get caught they will throw the book on you to scare away others. You can be charged by Unauthorized use of computer, Fraud and who knows what else. All of that to save four dollars on a ticket? When every station has cameras?

Re: The tiny chip that powers Montreal subway tickets

#77

Post by unholythree »

scrollaway wrote: post #74
cypherpunks01 wrote: post #63

My favorite household NFC usage? NFC alarm clock. Makes me get out of bed and tap my phone on a specific NFC tag placed somewhere around the house, in order to turn off the alarm. Then, I may as well wake up, since I'm already out of bed : ) It's a nice companion to help perform 'habit stacking' as Atomic Habits calls it. Want to do pushups right after waking up? Place an NFC card under your workout mat, so you're fo…

> Makes me get out of bed and tap my phone on a specific NFC tag placed somewhere around the house, in order to turn off the alarm. Neat, but is there an advantage between this and "Place the alarm clock further from the bed"?

The noise maker (alarm) is still close to him.

Re: The tiny chip that powers Montreal subway tickets

#79

Post by ComputerGuru »

kens wrote: post #25
bobthepanda wrote: post #3

This wasn’t super obvious to me until later in the article but this is about the single use tickets. Neat stuff, though I can’t say I love the concept of e-waste NFC.

I don't like the e-waste aspect either, but realistically, the chip is so minuscule that the amount of waste is trivial compared to almost anything else you might discard. The chip is literally the size of a grain of salt. The other factor is that people who use tickets regularly would use the rechargeable plastic cards, rather than the disposable tickets, so the amount of waste is reduced.

You are discarding both the chip and every consumable that went into making that chip, though.

Re: The tiny chip that powers Montreal subway tickets

#80

Post by cypherpunks01 »

scrollaway wrote: post #74
cypherpunks01 wrote: post #63

My favorite household NFC usage? NFC alarm clock. Makes me get out of bed and tap my phone on a specific NFC tag placed somewhere around the house, in order to turn off the alarm. Then, I may as well wake up, since I'm already out of bed : ) It's a nice companion to help perform 'habit stacking' as Atomic Habits calls it. Want to do pushups right after waking up? Place an NFC card under your workout mat, so you're fo…

> Makes me get out of bed and tap my phone on a specific NFC tag placed somewhere around the house, in order to turn off the alarm. Neat, but is there an advantage between this and "Place the alarm clock further from the bed"?

Not a huge advantage, but I'd say mostly range and flexibility. You may want to put the tag farther away than you could hear an alarm clock, if you want to go to another room. And you could customize the alarm so you're guided towards a different tag every day of the week, without needing multiple (or any) alarm clocks.
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