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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

#461

Post by solarpunk »

codewench wrote: post #432
Delk wrote: post #374

Earlier quoted context omitted.

I'm not sure that necessarily explains the need for single-use NFC tickets, though. There could be a more durable serial-use or permanent card with NFC that regular commuters could buy, and if those commuters are the vast majority of rush hour passengers, it might not be such a problem if single-use tickets had a slightly slower system. Of course that'd mean having two recognition mechanisms, so the operator might op…

Taipei has single use NFC tokens that people can buy, but they are non-disposable. Instead, they are coin shaped, and are deposited in the ticket machine at the end of the trip so they can be re-used.

COOL

Re: The tiny chip that powers Montreal subway tickets

#462

Post by KineticLensman »

jasonkester wrote: post #396
a-dub wrote: post #348

Earlier quoted context omitted.

NYC OMNY allows for direct payment from a debit/credit card via NFC at the turnstile. this has privacy issues but i think they're ameliorated if you use a smartphone. i think you can buy a transit payment card if you need one. no paper tickets. cool ephemera but pretty wasteful. would be pretty cool if/when we see a day where provably private cryptocurrency microtransactions allow for both real privacy and the 7 day…

I like London’s version of this. You can just tap your credit card or phone at any station, and it will even stop charging you after you rack up £8 in payments over the course of a day. Just pretends you had bought a day pass in the first place. Really leaves a good impression, knowing that they could have gouged you but chose not to.

Yes, super easy to use. And if you don't want to use a bankcard or phone you can buy a dedicated 'oyster' card and top it up as required. They all use the same card reader.

Re: The tiny chip that powers Montreal subway tickets

#463

Post by divbzero »

altacc wrote: post #346
solarized wrote: post #324

To peoples asking: "Why not just QR codes?" Again it's all about latency. QR codes take longer when you tap them at the gate: opening the app, waiting for the scanner to adjust, connecting to inet. While NFC handle these tasks almost instantly. A big difference in super busy places where queues are a nightmare. Again, this problem wouldn't exist if we can optimize WFH methods. We don't need to solving "physical probl…

In some places, like Oslo's metro, tram & bus systems, the solution is that there are no ticket barriers, you're trusted to have bought a ticket for your journey. There are occasional ticket checks with big fines for non-compliance.

Seattle’s light rail also works this way: no ticket barriers and occasional ticket checks.

Re: The tiny chip that powers Montreal subway tickets

#464

Post by [deleted] »

solarized wrote: post #324

To peoples asking: "Why not just QR codes?" Again it's all about latency. QR codes take longer when you tap them at the gate: opening the app, waiting for the scanner to adjust, connecting to inet. While NFC handle these tasks almost instantly. A big difference in super busy places where queues are a nightmare. Again, this problem wouldn't exist if we can optimize WFH methods. We don't need to solving "physical probl…

[deleted]

Re: The tiny chip that powers Montreal subway tickets

#465

Post by pizzalife »

ralferoo wrote: post #452
matsimitsu wrote: post #301

Earlier quoted context omitted.

In China, QR Codes are used for public transport too, and I found them just as fast as NFC readers (and faster than the slow readers used by the NS in The Netherlands)

Until you go to another city and discover that the local bus company has decided that instead of just letting you pay by Wechat pay or Alipay, you need to install their proprietary app to generate the QR code for the bus to scan, at which point the app then just turns it into a Wechat pay or Alipay transaction at the end. No benefit to the user, it just allows the bus company to extract all your PII in the process. A…

>Actually, I think part of the reason is that so they know who's on the bus in case it's involved in an accident

The CCP certainly do want to know who's on the bus, but not for the reasons you stated.

Re: The tiny chip that powers Montreal subway tickets

#466

Post by ak217 »

CraigJPerry wrote: post #227

QR codes seem like a better ticket medium. This is like a 100 bytes, a qr code can be over 2kb This is a cheap plastic substrate with ink printing over the top. A qr code is just ink - or some other even cheaper printing process if you prefer. This needs a specific ticket technology supplier over the next 10’s of years. QR codes can be drawn on screens or printed on paper and you can change suppliers for every compon…

Lots of others mentioned key downsides of QR codes that make them generally unsuitable for this purpose (they are stateless, trivially copied, easily fouled from repeated use, too slow because of fundamental optical constraints, require a 100% available centralized ledger/don't work while the reader is offline, etc. etc.) but I'd just point out that decades of R&D have gone into making these systems work well at scale at the busiest train stations in the world, and QR codes came up short. Here is a glimpse of early R&D efforts that went into this: https://www.jreast.co.jp/e/development/tech/pdf_6/tec-06-40-... - it covers some of the technical requirements these systems fulfill.

Re: The tiny chip that powers Montreal subway tickets

#467

Post by ck45 »

The article itself is a very interesting summary of the technology used.

As for the comments, there seems to be a big discussion on whether NFC or barcodes (includes QR codes) are the better technology for public transport ticket I have a completely different view: No matter what technology you are using, after having used public transport in multiple cities in Germany with the same flat rate tickets, I wonder if this could be feasible in every city or country. Just not caring about a ticket seems to be the most user friendly option. It seems to work well, but such a system would need to prove itself in areas where public transport is already quite crowded, like London.

Re: The tiny chip that powers Montreal subway tickets

#468

Post by kens »

qaisjp wrote: post #282
kens wrote: post #2

Author here for all your NFC chip questions :-)

I really enjoyed this read, thanks. In the footnotes you said: > One complication is that the counters have an "anti-tearing" feature for additional security Two questions: 1. Why is it a "complication"? Is it just that it makes the counters more complicated, or is there something frustrating about the counters? 2. I would love to learn more about how the anti-tearing feature works!

The problem is that if the user tears the card away from the reader in the middle of an update, that card can end up with corrupted data. This makes implementing the increment-only counters more complicated. For instance, the straightforward approach might hold 00 FF in two bytes. If you increment the counter by updating the low-order byte first, but the card gets torn away before you update the high-order byte, you end up with 00 00, and the counter has gone backward.

A simple way of preventing tearing is to have two copies of each counter; if there is tearing, then the two values will be different.

Looking at an NXP patent [1], they use a much more complicated approach, using a level of indirection. They write the new value to a different memory page and then update a pointer to the new page. There are various progress bits recorded along the way so they can roll back as needed.

[1]: https://patents.google.com/patent/EP3226141A1

Here's an article describing an attack on the anti-tearing feature: https://blog.quarkslab.com/rfid-monotonic-counter-anti-teari...

Re: The tiny chip that powers Montreal subway tickets

#469

Post by kens »

wiz21c wrote: post #439

FTA: > It's remarkable that these NFC chips can be manufactured so cheaply that they are disposable In our times, where we slowly understand that we have problems of resources and waste, I find it very disturbing that "disposable" is considered a positive achievement by the author.

No, I do not consider "disposable" to be a positive achievement. I consider it to be surprising and worthy of attention that NFC chips are so cheap that they are disposable.

Re: The tiny chip that powers Montreal subway tickets

#470

Post by dheera »

lxgr wrote: post #255
dheera wrote: post #101

Earlier quoted context omitted.

I believe Singapore's public transit does support tapping a credit card directly at the gates now, but there's an annoying step of having to register your card in advance on an app before it actually works. My guess is this might be because on-the-fly credit card authorizations still take too long. Waiting 3 seconds for an EMV contactless verification would seriously hold up the line at rush hour in a country where m…

That's odd. Most open-loop transit payment systems I know give new/unknown cards the benefit of the doubt, and put the card on a block list if it turns out to not be good for the fare that's eventually distributed to all readers. Are you sure that's true? Their website says otherwise: > Do I need to sign up for a SimplyGo account to use my contactless bank card for transit? You do not need to sign up for a SimplyGo a…

OK, it's confusing, I had seen some other information that suggested app registration was necessary. It seems that it's only necessary if you want to track your journeys which makes sense.
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