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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

#51

Post by lxgr »

Waterluvian wrote: post #16

On the topic of NFC: my iPhone ApplePay thing taps so much more reliably than any of my credit or debit cards. Is this because it has its own power supply and doesn’t have to first be powered up by the machine?

The primary reason is probably just that the secure element in more recent iPhones is probably just an order of magnitude more beefy than the IC in your physical cards.

Powering up the IC actually doesn't take long, but the processing itself can: Contactless payment transactions (mostly) use asymmetric cryptography, and old one at that too (usually RSA), so simply crunching the numbers takes these fairly underpowered ICs quite some time, even when they include cryptographic coprocessors.

Compare that with (symmetric key based) transit ticket authentication, e.g. for MIFARE DESfire or Japanese Felica cards: These usually use DES or AES, which is lightning fast in comparison.

Re: The tiny chip that powers Montreal subway tickets

#52

Post by kens »

ClumsyPilot wrote: post #38
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.

Indeed, I didn’t know what kind of ticket we are talking about - folks please include a picture and some context in your blogs, for people from other places and countries

The title says "Montreal" and the second photo in the blog post shows the specific ticket. I'm not sure what else I can do here.

Re: The tiny chip that powers Montreal subway tickets

#53

Post by b112 »

dheera wrote: post #35
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 feel like 99% of people would not benefit from single use public transportation tickets. Even if you are a tourist, if you use public transportation once, there is a high likelihood you will use it multiple more times, in which case it makes sense to get a regular card. Most systems let you return the card and get the deposit back if you'd like. Personally I collect the cards instead because I have a tendency to re…

I don't know how many times I've been in a city for a single day, or part of one, and have zero interest in spending precious minutes finding, buying, and returning a card.

Just let me pay with coins, or a credit card in seconds, with no return work.

Re: The tiny chip that powers Montreal subway tickets

#54

Post by amluto »

kens wrote: post #19
cypherpunks01 wrote: post #4

Earlier quoted context omitted.

How difficult is it to clone MIFARE Ultralight EV1 chips? You mention the UID is signed, can you simply copy this signature? Do you just need to buy one of the magical chips of the same design, that allow uid/serials to be written? What is the actual mechanism behind the DESFire and other secure NFC chips that prevents cloning?

I haven't really looked into the security aspects. I think that you could clone one of the Ultralight chips, but it wouldn't gain you anything because the security is in the backend. It's a lot like a printed concert ticket or boarding pass. You could print as many as you want, but the ticket is still good for just one admission. The DESFire and other secure chips contain a cryptographic key that you can't access. Wi…

In general, the card emulation devices (e.g. the chips in phones) try to avoid letting any arbitrary UID be set. This makes cloning these cards more difficult than it would otherwise be. It’s not terribly difficult to find devices (USB-connected things and battery-less cards) that do allow arbitrary UIDs to be set, though.

Re: The tiny chip that powers Montreal subway tickets

#56

Post by Reason077 »

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.

> ”the chip is so minuscule that the amount of waste is trivial”

It does add significant costs to the transport system. Single-use NFC cards must cost at least a few cents to produce and dispense, which adds up when you’re talking about hundreds of thousands or millions of rides every day.

Even reusable NFC cards are costly in terms of providing all the infrastructure to support them: software, servers, enough top-up machines in stations to handle peak demand, commissions to retailers selling the cards, extra staff to deal with customer support, delays and congestion caused by top-up/ticketing queues, etc.

That’s one reason London’s TfL has been pushing everyone to just use their bank-issued contactless credit/debit cards (or NFC-enabled phones) for years now.

It’s also more convenient, of course, to never have to worry about your balance or recharging the card.

Re: The tiny chip that powers Montreal subway tickets

#57

Post by astrobe_ »

kens wrote: post #10
webwielder2 wrote: post #5

So how much more powerful is this chip than the ones NASA used in the the Apollo program?

I think this chip is implemented with a state machine rather than a processor, so it's meaningless to compare their processing power. The Apollo Guidance Computer had about 17,000 transistors, while I estimate that the NFC chip has about 45,000 transistors. So the NFC chip has more complexity, but the same order of magnitude.

For the fun of it, what about radiation hardening ?

Re: The tiny chip that powers Montreal subway tickets

#58

Post by josephcsible »

amluto wrote: post #54
kens wrote: post #19

Earlier quoted context omitted.

I haven't really looked into the security aspects. I think that you could clone one of the Ultralight chips, but it wouldn't gain you anything because the security is in the backend. It's a lot like a printed concert ticket or boarding pass. You could print as many as you want, but the ticket is still good for just one admission. The DESFire and other secure chips contain a cryptographic key that you can't access. Wi…

In general, the card emulation devices (e.g. the chips in phones) try to avoid letting any arbitrary UID be set. This makes cloning these cards more difficult than it would otherwise be. It’s not terribly difficult to find devices (USB-connected things and battery-less cards) that do allow arbitrary UIDs to be set, though.

> the card emulation devices (e.g. the chips in phones) try to avoid letting any arbitrary UID be set.

I can't think of a much worse way to do security. That feels like trying to flood the market with lockpicks that don't work instead of making a more pick-resistant lock.

Re: The tiny chip that powers Montreal subway tickets

#59

Post by tzot »

muxator wrote: post #26
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.

Agreed! In Rome for some time now one can top up his paper NFC ticket; there is no reason to throw it away.

Yep, the ones in Athens can be refilled too.

Re: The tiny chip that powers Montreal subway tickets

#60

Post by mig39 »

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.

The ones I've used in the Netherlands and Portugal are similar, but can be refilled.

In Portugal, you pay extra for the initial ticket, but subsequent uses are cheaper, because you are using the same physical ticket.

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