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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

#501

Post by efreak »

grishka wrote: post #499
DiogenesKynikos wrote: post #483

Earlier quoted context omitted.

It only has to process requests inside a single station, and then periodically sync up with a central server. This doesn't sound difficult at all.

This is indeed how systems around the world do it for NFC tickets. The problem with QR codes is that they're very easy to copy, so the potential for abuse with this approach is much higher. What's to stop people from using the same ticket on two different stations within the sync period?

The QR code can encode (or the system can track, or both) any combination of origin, destination, expiration (or purchase time + validity period), ticket number, etc. Check with the local server that the ID exists with the given information and that the ticket isn't expired, then allow the user through, and the server marks that ticket number as used. If the origin doesn't match the current station, the ticket is expired, or the ticket is used, don't let the user in.

Re: The tiny chip that powers Montreal subway tickets

#502

Post by grishka »

efreak wrote: post #501
grishka wrote: post #499

Earlier quoted context omitted.

This is indeed how systems around the world do it for NFC tickets. The problem with QR codes is that they're very easy to copy, so the potential for abuse with this approach is much higher. What's to stop people from using the same ticket on two different stations within the sync period?

The QR code can encode (or the system can track, or both) any combination of origin, destination, expiration (or purchase time + validity period), ticket number, etc. Check with the local server that the ID exists with the given information and that the ticket isn't expired, then allow the user through, and the server marks that ticket number as used. If the origin doesn't match the current station, the ticket is exp…

So you would have to buy a ticket every time you go somewhere. That would work for tourists, sure, assuming there are vending machines that can print those QR codes. But it would not work for locals (imagine everyone buying tickets during a rush hour), and even for some tourists, it would be a nuisance. If you're visiting a city and you know you're going to take the subway N times, you would just buy N tickets, but with this system no such thing is possible.

And what about all those transfer discounts some cities have? Like if you're taking the subway and a bus within some timeframe, you still only pay once.

Re: The tiny chip that powers Montreal subway tickets

#503

Post by Reason077 »

rtpg wrote: post #274
Reason077 wrote: post #207

Earlier quoted context omitted.

Yes, the TfL system does a partial authorisation. It checks the card is valid and not blocked etc but doesn’t necessarily do a real-time authorisation all the way to the issuing bank. If you try to use a card that is valid but has no available balance/credit, it might work for the first ride but then be blocked when you try to use it for the return trip. Fares are batched throughout the day and you are charged once,…

Wonder how they block the card, my impression was that tokenization was meant to make it harder for card chargers to be able to track a card through multiple taps like that.

TfL not only gets your Apple Pay device account number (DAN), but can also associate it with the primary card number (PAN). Both magically appear if you add the primary card to your online TfL account and have used the associated Apple Pay device with TfL before.

Re: The tiny chip that powers Montreal subway tickets

#504

Post by bboygravity »

gruez wrote: post #31
bboygravity wrote: post #29

Earlier quoted context omitted.

The chip is the size of a grain of salt, but there's a relatively huge antenna inside made of conducting material (metal?) and glue and all that.

all of that is probably negligible compared to how much disposable foil is used for cooking or packaging.

The question is whether it's negligible compared to good old fashioned paper tickets.

Re: The tiny chip that powers Montreal subway tickets

#505

Post by wkjagt »

I can't help but feeling a little sad about single use electronics. Not even from an environmental perspective (though there's that too) but just the fact that there's some pretty cool electronics, doing digital and analog stuff, wireless communication etc, that does it's thing once, and then never again.

Re: The tiny chip that powers Montreal subway tickets

#506

Post by a-dub »

delfinom wrote: post #373
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…

Crypto isn't private as traceability is an inherent requirement for crypto to operate. Anyway with OMNY. You just buy a OMNY card and load it with cash if you want privacy. They are being slow to roll the vending machines for these out due to vendor issues but it's growing and they can't discontinue the MetroCard until they have all the vending machines in place.

> Crypto isn't private as traceability is an inherent requirement for crypto to operate.

monero is a counterexample to this.

i wonder how many organizations that do payroll see a timestamp and location when you tap a credit card at an omny reader?

maybe it's fine and can be solved with regulation, but honestly it seems a little not great.

Re: The tiny chip that powers Montreal subway tickets

#507

Post by bunderbunder »

efreak wrote: post #500
bunderbunder wrote: post #494

Earlier quoted context omitted.

Those are more for single rides by people who rarely or never use the transit system. I've had the same Carte Opus for years and just bring it with me and refill whenever I visit Montreal. And the disposable paper cards are being phased out. I'm not sure when the rollout will be, but Montreal is currently working on upgrading the system to allow people to just tap-to-pay at the turnstiles using their phones or compat…

> Montreal is currently working on upgrading the system to allow people to just tap-to-pay at the turnstiles using their phones or compatible credit and debit cards. > Which is not something that you could do with a QR system I've got several apps that display QR codes on the screen for an external reader. One of them is for my health insurance id card (a simple 10 digit number), another shows my COVID vaccination st…

By tap-to-pay, I mean you need no special apps, you need no special accounts, any of that. You can pay with any physical credit or debit card that supports tap-to-pay, or you can use any credit or debit card you have loaded into your phone.

With a QR code like that, people still need to install an app, set up an account, etc. It's just a lot more friction. In cities where I can tap-to-pay, getting set up to ride a bus or train for the first time takes literally zero time; I'm already set up. If I need anything special - apps, accounts, system-specific QR codes, etc - then the setup time instantly goes up to a minimum of 10 minutes. It's a relatively large barrier to entry for infrequent riders, and ultimately serves to discourage use of public transit.

Re: The tiny chip that powers Montreal subway tickets

#508

Post by rswail »

hgomersall wrote: post #294
rswail wrote: post #289

Earlier quoted context omitted.

I've worked in public transport ticketing for the past 30 years including the first system outside Japan (Hong Kong's Octopus). The problem with QR codes: 1. If they're printed, they can be copied. 2. "Dynamic" QR codes can be screenshot. 3. They're read-only (by definition) 4. Readers are slow, require good orientation by the user. NFC is good because it's read/write, has a ~10cm range, the larger cards can hold up…

I don't think the suggestion is the QR code contains the ticket info, but that the QR code is the unique tag into the back end virtual ticket system. 1 to 3 are not relevant in that context, and 4 isn't borne out in my experience with modern readers (they're used in the bar code mix at parkrun and they read time is vanishingly fast with a smart phone, generally better than barcodes). The number of bits might increase…

The problem with expecting a "unique tag into the back end" is that these systems have to work offline.

The QR codes are significantly slower to read than NFC.

I've built both NFC and QR (and ye olde fashioned magnetic stripe) ticketing systems.

Re: The tiny chip that powers Montreal subway tickets

#509

Post by rswail »

hgomersall wrote: post #490
bunderbunder wrote: post #478

Earlier quoted context omitted.

NFC doesn't necessarily create any additional e-waste. In Chicago we have an NFC system, and people typically just link their phone to their account and use that to pay. I still use a physical card - so that I have a backup option in case something happens to my phone - but even there the volume of waste is trivial. I've had my current transit card for ages, and it doesn't expire until 2037. It's possible that the on…

Well, yes, but the article is about a disposable nfc ticket.

On rail systems with gates, these disposable "ultralite" RFID tickets are usually put through the old slot that used to take magentic tickets.

Exit gates usually capture the ticket on exit when it has been used up (ie single journeys, or after the number of trips encoded on the ticket).

These can (and are) recycled numerous times.

Re: The tiny chip that powers Montreal subway tickets

#510

Post by rswail »

sverhagen wrote: post #298
hgomersall wrote: post #294

Earlier quoted context omitted.

I don't think the suggestion is the QR code contains the ticket info, but that the QR code is the unique tag into the back end virtual ticket system. 1 to 3 are not relevant in that context, and 4 isn't borne out in my experience with modern readers (they're used in the bar code mix at parkrun and they read time is vanishingly fast with a smart phone, generally better than barcodes). The number of bits might increase…

> and 4 isn't borne out in my experience To bolster your point, aren't there whole countries where stores and street sales float on top of QR codes?

Those QR codes are validated online.

Transit has to work offline.

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