[HN Gopher] The tiny chip that powers Montreal subway tickets
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The tiny chip that powers Montreal subway tickets
Author : todsacerdoti
Score : 298 points
Date : 2024-06-23 17:22 UTC (5 hours ago)
(HTM) web link (www.righto.com)
(TXT) w3m dump (www.righto.com)
| kens wrote:
| Author here for all your NFC chip questions :-)
| cypherpunks01 wrote:
| 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?
| kens wrote:
| 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. Without the key, you can't make a
| clone of the chip. The cryptography provides authentication
| and encryption that you don't get with the cheap Ultralight
| chip.
|
| I think this is all market segmentation; they don't put more
| security into the Ultralight chip because they don't want to
| cannibalize their higher-end sales.
| lxgr wrote:
| 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.
| kens wrote:
| 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.)
| lxgr wrote:
| 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.
| szundi wrote:
| You have to hang out to get the id of a simple 125khz tag
| too - this is what cloning means
| amluto wrote:
| 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.
| josephcsible wrote:
| > 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.
| amluto wrote:
| I imagine this is because the locks contain chips from
| NXP (PN532 chips), the name-brand MIFARE chips are made
| by NXP, and the lock picks (also PN532 chips!) are made
| by NXP.
| jeffbee wrote:
| 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.
| cypherpunks01 wrote:
| Most people who live in Boston use the reloadable CharlieCard
| (https://www.mbta.com/fares/charliecard) - these report as
| Mifare Classic 1k, which is a similar chip
|
| There are single-use fares as well, the "CharlieTicket" that
| you might've encountered.
|
| More CharlieCard NFC info:
|
| https://medium.com/@bobbyrsec/operation-charlie-hacking-
| the-...
|
| https://media.defcon.org/DEF%20CON%2031/DEF%20CON%2031%20pre.
| ..
| jeffbee wrote:
| Yeah I figured but you can't buy a charliecard online to
| load into your smartphone wallet, and I only needed it the
| once, and since it took more than an hour to get to
| Cambridge due to some combination of circus acts I used
| Blue bikes for the remainder of the day.
| cypherpunks01 wrote:
| Ah yes, it's not quite there, but almost. Contactless
| payment directly at the turnstile is coming to Boston
| MBTA this year, I believe. Like how NYC works now, where
| you can just use your credit card for entry.
| chgs wrote:
| This is the London system we've had for a decade, it was
| licensed to other areas a few years ago.
|
| I found myself in Paris having to cross the other day and
| forgot how terrible the old way of buying tickets was,
| amazed that it's still the norm in so many cities
| jcynix wrote:
| 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.
| modeless wrote:
| I am interested in the plastic layer with conductive traces for
| the antenna. How are these made? Do you know of a source that
| talks about the production process for them?
| kens wrote:
| I don't know personally about the antenna manufacturing, but
| one web page talks about printable conductive silver ink for
| producing RFID antennas.
| https://www.sunchemical.com/product/printed-antenna/
| politelemon wrote:
| Could someone just use an nfc enabled phone to get it to act as
| a ticket?
| lxgr wrote:
| For MIFARE Ultralight, yes - it's essentially just a bearer
| token with no encryption/authentication. I believe there's a
| password mechanism, though, which might just be good enough
| for single-use tickets. That password can be
| derived/diversified from the card's serial number, making
| such a scheme still significantly better than e.g. simple QR
| codes.
|
| MIFARE Ultralight C and larger/more expensive chips allow
| challenge-response authentication, making them pratically
| uncloneable. These are usually used for reloadable and
| monthly passes.
| numpad0 wrote:
| Layer 3 and down yes, 4 and up depends
| ak217 wrote:
| Thanks for the write-up.
|
| How does this fit into the broader NFC ecosystem? What do other
| big metro systems like Omny, Clipper, Smartrip etc use? Apple
| and Google seem to implement some NFC protocols in their
| devices but in a much more programmable way, how does that
| work? Is the protocol used in credit cards related at all? And
| how do these relate to Felica, the system used everywhere in
| Japan (which was in the news for a while because the factory
| where they made the chips burned down and they had a chip
| shortage - giving Apple an opening to move into the market with
| iPhone NFC)?
| kens wrote:
| That seems like a question for @lxgr :-)
|
| As far as I can tell, the NFC ecosystem is a mess of
| competing, incompatible protocols from different companies,
| as well as incompatibilities for historical reasons. For
| example, Clipper uses MIFARE DESFire, which is the more
| secure sibling of the Ultralight chip that I examined.
| Washington's SmarTrip cards use MIFARE Plux X. New York
| City's OMNY, on the other hand, is apparently built on top of
| the Mastercard payment network using EMV. Montreal's
| rechargeable OPUS card (not the disposable one I examined)
| uses the completely different Calypso standard. FeliCa was
| developed in Japan along a different path and has a different
| standard (NFC-F vs NFC-A) with different modulation,
| protocol, and data rates. The NFC chips used in phones try to
| be compatible with as much as possible. These NFC systems all
| use the same 13.56 MHz frequency, so the radio hardware is
| compatible across them.
| Tijdreiziger wrote:
| How and why did you learn about this topic? :)
| Tijdreiziger wrote:
| > Is the protocol used in credit cards related at all?
|
| In e.g. London and the Netherlands, the readers were upgraded
| to support tapping in and out with a debit/credit card or
| Apple/Google Pay.
|
| However, Apple also seems to have an 'Express' mode, which
| even works when the battery is empty ('Power Reserve').
|
| It seems to me that there must be three protocols: the one
| for the disposable and stored-value tickets (ISO 14443?), EMV
| for debit/credit/Apple Pay/Google Pay, and Apple Pay Express.
| lmz wrote:
| EMV (specifically EMV contactless) is also based on ISO
| 14443, it's more like an application layer protocol on top
| of it.
|
| Apple Pay Express is just Apple Pay without the need for
| the full system UI: "If iOS isn't in use because iPhone
| needs to be charged, there may still be enough power in the
| battery to support Express Card transactions." it interacts
| the same way as the physical card equivalent (otherwise
| they would need a reader upgrade).
| teruakohatu wrote:
| That was a god read, thank you.
|
| Do you have any insight into the economics of this in general
| compared to other disposable solutions. Are manufacturing old
| school magnetic stripe tickets, or just optical
| scanning/barcodes a lot cheaper?
|
| I imagine magnetic stripes have a higher failure to read rate
| at the turnstile causing issues, while both them and optical
| scanning requires the ticket to be inserted into the machine,
| adding complexity and moving parts.
| kens wrote:
| I couldn't find a nice price breakdown. I'd expect the
| magnetic stripe tickets to be cheaper to manufacture, but
| since the NFC tickets cost pennies, there isn't a lot of
| money to save. I agree with you that magnetic stripes would
| have a much higher maintenance cost due to the mechanical
| aspect and the read/write head. Optical scanning seems less
| likely to work the first time, based on my experience with
| airplane checkins. NFC is probably the best from an ecosystem
| perspective since it can work with credit cards and phones as
| well. NFC readers are probably the cheapest since they are
| produced in large volumes for credit card point of sale.
| seizethecheese wrote:
| I've been curious about the orientation of these devices. For
| examples, if I want to track an item's presence in a box, would
| I have to coat the entire item in these chips to get one to be
| in the right orientation?
| kens wrote:
| I think it depends on the type of antenna. A linearly
| polarized RFID antenna is sensitive to the tag's orientation,
| but a circularly polarized antenna is less sensitive to
| orientation. Systems can also use more than one RFID antenna
| to get better coverage.
| maaarghk wrote:
| Not an NFC chip question, but what kind of microscope do you
| need to get silicon photos of a chip so tiny?
| kens wrote:
| The trick is to use a metallurgical microscope, which shines
| the light down through the lens. A regular microscope
| illuminates from below, which works fine for cells, but not
| for opaque chips.
|
| Specifically, I use an AmScope ME300TZB-2L-10M microscope,
| which my friends consider an entry-level microscope, but it
| works for my needs.
| bobthepanda wrote:
| 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.
| adolph wrote:
| It isn't different from other anti-counterfeiting measures, the
| printing just happens to be really small and electrically react
| to certain frequencies.
|
| Part of the "software eating the world" story is the decreased
| cost of precision that enabled the hardware substrate of
| software to be inexpensively and ubiquitously included in any
| mass produced object.
| kwhitefoot wrote:
| Assuming that it doesn't become litter on the street what is
| the actual impact of such waste?
| Teever wrote:
| All of the waste that went into producing it of course.
|
| IC fabrication produces a lot of chemical waste, and I would
| imagine that these ICs aren't fabbed in a place that has a
| great track record on pollution.
| kens wrote:
| 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.
| bboygravity wrote:
| 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.
| gruez wrote:
| all of that is probably negligible compared to how much
| disposable foil is used for cooking or packaging.
| lxgr wrote:
| On one hand it is probably small in comparison, but on
| the other hand, it seems much more feasible to reuse
| transit ticket ICs than e.g. food packaging.
|
| Many transit agencies do explicitly incentivize reuse,
| e.g. by offering cheaper fares using a reloadable
| contactless card and often charging a deposit for that
| card.
|
| Even then, many of these systems have been struggling due
| to the IC shortage, given the low margins these single-
| use tickets have to operate on. In some Asian countries,
| including Japan and Malaysia, it was tricky to get a new
| transit card for several months or even years, even
| though there is a deposit charge.
| ximus wrote:
| I don't know about justifying or rationalising waste by
| pointing to a greater source of waste.
| wkat4242 wrote:
| Yeah but also the antenna and I wonder how many chemicals are
| used in the lithography process.
| Reason077 wrote:
| > _"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.
| ComputerGuru wrote:
| You are discarding both the chip and every consumable that
| went into making that chip, though.
| bobthepanda wrote:
| I don't really see why a chip is needed at all for single use
| tickets. Those have existed forever and there are a plethora
| of non-chip options ranging from the simple holepunch to the
| optical printed barcode or QR code.
| muxator wrote:
| Agreed! In Rome for some time now one can top up his paper NFC
| ticket; there is no reason to throw it away.
| tzot wrote:
| Yep, the ones in Athens can be refilled too.
| dheera wrote:
| 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 revisit cities years into the future. I just wish
| cities wouldn't make their cards expire so damn quickly.
| Wuhan's metro is nice, the cards don't expire until 10 years
| later. But I've found Singapore and Taipei expire within 3
| years and you lose your stored money.
|
| I have this "brick" of public transit cards for about 20
| cities. It feels powerful. I kind of wish I could just swipe
| this brick in any city and just go. Unfortunately they all
| interfere with each other.
| bbarnett wrote:
| 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.
| dheera wrote:
| 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 most people live by
| public transit.
|
| If I were to guess, the registration is probably what
| enables them to pre-authorize a credit line and allow you
| to tap in in a fraction of a second.
| kccqzy wrote:
| Credit cards do not require online authorization.
| bbarnett wrote:
| Interesting, and this hypothesis shows why twmp cards
| might be preferred.
|
| I have no issue with temp cards, if I can buy them right
| at the pickup location. I once flew into a place late at
| night, and only stores had cards to buy, and all were
| closed.
|
| Duh.
| dheera wrote:
| Yeah that's a stupid system and I've seen it in many
| places. Being asked to go to <some random convenience
| store> to get the official public transit card, even the
| dude at the station couldn't sell me one.
|
| The vending machines at every station should be capable
| of directly vending public transit cards. I think most of
| the better systems around the world do work that way.
| ClumsyPilot wrote:
| 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
| kens wrote:
| 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.
| bobthepanda wrote:
| Background information in an article is normally presented
| first.
|
| Ticket in english sometimes refers to a season or monthly
| ticket, so it's pretty ambiguous.
| mig39 wrote:
| 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.
| webwielder2 wrote:
| So how much more powerful is this chip than the ones NASA used in
| the the Apollo program?
| kens wrote:
| 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.
| astrobe_ wrote:
| For the fun of it, what about radiation hardening ?
| kens wrote:
| The Apollo Guidance Computer would be more radiation-hard,
| due to its large transistors and magnetic core memory.
| BOOSTERHIDROGEN wrote:
| I would like a comprehensive analysis of FeliCa.
| lxgr wrote:
| Same here! It seems like a fascinating system, especially in
| the federated way in which it's being used by various Japanese
| transit agencies and issuers. Compared to MIFARE, it was
| definitely ahead of its time.
|
| Unfortunately, most things I could find are in Japanese, as
| expected; I suspect that the really interesting parts aren't
| public, as usual in this industry (there's still a lot of
| belief in security by obscurity, even if the systems actually
| don't need it).
|
| Singapore's CEPAS seems very similar conceptually to Felica (at
| least in application, in that there's multiple issuers of
| stored-value cards with interoperability), and the
| specifications for that seem to be available for purchase, but
| I'm not curious enough to bite that bullet yet :)
| piombisallow wrote:
| The diameter of a neuron's axon is about 1 mm, this is getting
| close to biological levels of miniaturization.
| therein wrote:
| It is using a relatively old manufacturing process. It may be
| small but it is because modern chips are small, not because
| this is a feat of engineering where they've achieved incredible
| compute densities.
| phoebos wrote:
| It's small compared to the size of the card, sure, but not
| small for typical modern lithography techniques.
| localfirst wrote:
| 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 (newer hyundai rotem
| cars, old ones: https://www.youtube.com/watch?v=W_BoeXqaV9c)
|
| - Montreal subway does not cover the entire region like
| Vancouver's skytrain. Getting around is difficult without uber.
| Road conditions are horrible (pot holes remain unfixed for
| decades, city went broke hosting olympics long time ago), I just
| shudder how you can get around during the winter.
|
| But the biggest shock was that in some instances, it was _faster_
| for me to walk then walk to the station and wait for the subway.
|
| - Arriving at YVR: Skytrain runs directly from airport to a
| satellite city where its numerous public buses cover almost the
| entire MV. I could just tap through the toll gate with my credit
| card and wait for a bus which arrives on time quite frequently.
|
| - Arrriving at YUL: Have to take a bus from airport for 30
| minutes to Montreal but doesn't seem to respect time schedule.
| Got off somewhere in Montreal I don't remember (there was a large
| open artsy area) tried to wait for a bus but never came, gave up,
| got uber.
| osnium123 wrote:
| In addition to how hosting the Olympics hurt Montreal
| financially, there was substantial tax revenue loss from the
| trend of corporate headquarters moving from Montreal to Toronto
| staring in the 1960s due to Francophone policies.
| dgudkov wrote:
| >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.
| kens wrote:
| Strangely enough, I used the ticket in the article for the
| REM train (from Du Quartier, where I was staying).
| nsguy wrote:
| When I visited Montreal I mostly walked and used their rental
| bicycle. I did take a few subway rides and being from Vancouver
| it didn't leave any specific impression on me one way or the
| other - I got where I needed to get to (some suburb).
|
| The Skytrain to YVR is indeed very nice - built for the winter
| Olympics. Maybe not as "connected" as some European airports
| but quite convenient.
|
| The problem with transit in Vancouver is that most of it is
| rays emanating from downtown, i.e. you have fairly decent
| (though IMO worse than most large European cities) transit if
| you need to get downtown but it's terrible useless if you need
| to get across. My work used to be 20 minutes drive time, >2
| hours transit time.
|
| Skytrain doesn't exactly cover the entire region, as you get
| further away from the downtown core the coverage gets much
| spottier until when you get far enough (but still part of metro
| Vancouver) it's non-existent.
|
| There are certainly times when buses don't show up on time. I
| take transit these days to work and back and I would say
| something like 30% of the time the bus isn't on time. About 5%
| of the time the bus I'm supposed to take just never shows up.
| Waterluvian wrote:
| 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?
| adolph wrote:
| Additional conjecture: a device with upgradable software can
| take advantage of updates to readers and protocols. Whereas the
| physical card is stuck at the version it was created with.
| kens wrote:
| NFC supports passive mode (where one side is powered and the
| card is not) and active mode (where both sides are powered).
| So, yes, your phone is probably more reliable because it
| provides a powered data transmission.
|
| An NFC card doesn't actively transmit data. Instead, it sends
| data using "load modulation", where it switches a load across
| the antenna to change how much power it absorbs. The
| transmitter can detect this change in power, but the signal is
| extremely weak (80 decibels below the transmitted signal), so
| it's amazing that it works at all.
| Waterluvian wrote:
| That's insane. And yet when I see what we can do with coax or
| twisted pair, I anticipate we'll get to gbps speeds one day.
| :)
| lxgr wrote:
| The iPhone doesn't actually use NFC's peer-to-peer/"active"
| mode (since contactless payments aren't an NFC application;
| see my other comments on that), but it does specifically
| include an NFC "field amplifier" IC (shown in some iFixit
| teardowns), which most other smartphones and of course all
| physical cards/tags lack.
|
| This does mean that iPhones can't do cool tricks like booting
| up the secure element purely from the field with a completely
| dead battery though that some earlier Android and Windows
| Phones could do (or at least Apple has intentionally
| deactivated that capability for a more consistent/secure
| experience) :)
| lxgr wrote:
| 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.
| justusthane wrote:
| This is fascinating. We were just in Europe where we experienced
| these tickets for the first time. I had trouble with them; I was
| trying to figure out how to scan them because it never occurred
| to me that they might contain an NFC chip.
|
| My wife, on the other hand, who is not at all technical, took it
| for granted that you would tap them and immediately figured it
| out intuitively.
| hammock wrote:
| Where do you live? Chicago has had these contactless paper
| tickets since 2013
| cbhl wrote:
| Atlanta has been using a form of these contactless paper
| tickets since 2006.
| szundi wrote:
| Romans have used tickets before AD, guy at the gate checked
| it without any contact
| justusthane wrote:
| Thunder Bay, Ontario. Pop. 110k. We still have the sort of
| carnival-style paper tickets. I would guess that most smaller
| cities don't have fancy NFC tickets.
| hammock wrote:
| I'm surprised you have a subway at all
| justusthane wrote:
| We don't, we have a bus line.
| marssaxman wrote:
| That's funny - I'm sure I would have shared your confusion, as
| all tappable objects in my world are made of plastic. I wonder
| how your wife thought of it?
| TacticalCoder wrote:
| > ... as all tappable objects in my world are made of plastic
|
| yup in mine plastic and metal but not paper.
| markus_zhang wrote:
| I have found the same thing with my wife. I'm a technical
| person, but I'm extremely bad with tools and such, including
| the ticket thing. If no one shows me how to use it I'll
| probably figure out a way to insert it somewhere. My wife won't
| have any problem with this and other small tools.
|
| The same thing with IKEA: I always rely on the manual and just
| blindly follow the instructions, and gets very frustrated if
| the instructions miss one step.
| II2II wrote:
| > The same thing with IKEA: I always rely on the manual and
| just blindly follow the instructions, and gets very
| frustrated if the instructions miss one step.
|
| Following instructions is a good thing. Plenty of people
| damage stuff when putting it together since it looks obvious,
| but they usually miss critical details. I would imagine that
| the people who designed the card scanners had to put a lot of
| thought into their design simply because they know many
| people won't read instructions and would do as you suggest:
| figure out a way to insert [the card] somewhere.
| TheJoeMan wrote:
| Does the card not have the three-arcs nfc symbol? Similar to
| the wifi symbol. To me the fake printed dip-chip is more
| confusing!
| kens wrote:
| No, the card doesn't have any symbols like that. It does have
| a pictogram of the card getting tapped on a reader, along
| with the text "Apposez sur le lecteur".
| michaelt wrote:
| Most metro stations have a much simpler way for travellers to
| figure out what to do: of loads people who _do_ know how it
| works, ahead of and beside you.
| ghaff wrote:
| It's getting better but, in my experience, once metro
| systems got away from manned booths and tokens, the systems
| worked fine for commuters but led to lots of fumbling and
| long lines for tourists.
|
| Trains in the UK still have a certain amount of "Which of
| these tickets/receipts go where?" while a line of irritated
| locals is building up behind you. Fortunately, also being
| the UK, someone will help you if you're struggling with
| something sooner rather than later.
| devl547 wrote:
| All Moscow public transport powered by these chips (actually it
| was, nowadays the chips we use are clones, made in Russia itself)
| - trains, metro and buses.
| thriftwy wrote:
| For a few years now, you may usually do a contactless card
| payment - just tap your bank (debit or credit) card. The fare
| is often higher but so is convenience.
|
| Back around 2010 I remember reading these accusations that
| significant part of revenue went directly to Mifare for the
| massive number of chips.
|
| And for single rides, some of Metro systems still use these
| steampunk brass tokens. Sometimes, less authentic plastic.
| 1oooqooq wrote:
| every single transportation system that uses disposable nfc
| are definitely making a ton of money for the vendor.
|
| and every transportation system that pretends to run as a
| profit center and not a cost center also makes ton of money
| for the vendors.
| thriftwy wrote:
| Building roads and selling cars, though, also makes an
| awful lot of money for the vendors.
| Tijdreiziger wrote:
| In the systems I've ridden, there's usually some kind of
| plastic stored-value card for regular riders, and the (more
| expensive) disposable tickets are only used by occasional
| riders.
| amluto wrote:
| > Presumably, the makers thought that making the card look like a
| smart card would help people understand it. The card actually
| uses an entirely different technology.
|
| It's kind of the same, though. The physical communication layer
| is different, but the higher protocol layers are basically
| identical. Smart cards with contacts follow ISO 7816. These
| MIFARE contactless cards are ISO 14443 Type A cards, and their
| protocol follows ISO 7816-4.
|
| This shouldn't be terribly surprising -- the entire ecosystem
| built for smart cards with contacts wants to support contactless
| cards with minimal changes, and this includes the host software,
| the readers, and the logic in the cards. There are even plenty of
| devices where the same device supports contact and contactless
| uses -- plenty of credit cards, bank cards, and FIDO devices are
| like this.
|
| This is analogous to WiFi and wired Ethernet. They're have very
| different physical layers, but they are logically compatible, and
| the same software supports both.
| lxgr wrote:
| Only ISO 14443-4 uses the same protocol as ISO 7816 (another
| way of saying this is that ISO 14443-4 represents the higher
| layers of ISO 7816 over a different physical interface),
| though.
|
| MIFARE Ultralight does not actually implement
| 14443-4/7816/"smartcard"-style APDUs; it's significantly
| simpler, since the ICs are much less powerful.
|
| To make things more confusing, _some_ MIFARE ICs really do
| implement ISO 14443-4 (e.g. their fixed-function MIFARE DESfire
| cards, and their programmable smartcard ICs like SmartMX), but
| not all of them.
| lxgr wrote:
| > There are multiple NFC standards with differences in speed,
| protocol, and range, including NFC-A, NFC-B, NFC-C, NFC-F, and
| NFC-V. The MIFARE Ultralight cards use NFC-A, which is defined by
| the standard "ISO/IEC 14443 Type A".
|
| Pet peeve: Calling these chips "NFC" is a bit misleading. NFC-A
| isn't defined by ISO 14443-A, but builds on it.
|
| NFC is an umbrella standard that defines a way of storing
| structured data on a wide variety of existing contactless IC
| technologies (including, but not limited to ISO 14443) and
| products (such as NXP's various MIFARE chips, which in turn are
| based on various layers of ISO 14443 up to -4).
|
| For the concrete example, it's correct to say that one possible
| implementation of an NFC-A tag is MIFARE Ultralight (that would
| be a NFC forum type 2 tag), but neither is NFC the only thing you
| can do with MIFARE Ultralight (and this transit use case almost
| certainly doesn't put an NDEF container on the ticket), nor is
| this the only type of tag you could use for NFC.
| moralestapia wrote:
| >NFC is an umbrella standard that defines a way of storing
| structured data on a wide variety of existing contactless IC
| technologies [...]
|
| Yeah, then it's appropriate to call this NFC.
| lxgr wrote:
| Except that the highest layers in that stack is not used by
| many contactless systems. As an analogy, you wouldn't call
| HTTP or TCP "web protocols" either, even though the web uses
| both (but it can also run on QUIC, which is UDP, and you can
| do non-web-things via HTTP).
|
| Importantly, NFC standardizes a way of storing structured
| data like URLs or phone numbers on NFC tags; transit tickets
| most likely don't use tags in that way.
| mschuster91 wrote:
| > 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 provisioned at the factory
| with a unique private / public key pair, and the public key gets
| signed by the factory. Then, to verify authenticity, the terminal
| gives some random nonce, the card signs it using its private key,
| and the terminal verifies that against the factory's public key.
|
| > Even so, there were a couple of times that I lost track of the
| chip and had to check some specks under the microscope to
| determine which was the chip and which were dirt.
|
| That is the really amazing part for me. We as humans have
| difficulty handling them, but how on earth does a machine even
| _manufacture_ these, much less orient them consistently for the
| bond process to work?!
| lxgr wrote:
| > The problem is, they can be just as easily cloned.
|
| Not if the validation system uses the password feature of
| MIFARE Ultralight. For single-use tickets, which are
| invalidated immediately after being read, this can be good
| enough and is much more lightweight on the IC side.
| chx wrote:
| 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?
| mschuster91 wrote:
| The thing is, you have to do it only once, and then the
| clones and knockoffs come.
|
| Like what, there's Tiktoks advising young dumbasses precisely
| what they need to steal and joyride cars.
| ForHackernews wrote:
| > Like what, there's Tiktoks advising young dumbasses
| precisely what they need to steal and joyride cars.
|
| Yeah, because cars are valuable and joyriding a stolen car
| is impressive and cool to lots of teens. Getting a free
| ride on the bus is like negative street cred.
| GuB-42 wrote:
| > If you want actual security, you have to go for a challenge-
| response scheme
|
| Another option is to just store used UIDs in a database. In
| fact, you could do a system with only UIDs. For a single use
| ticket, validate the UID signature and mark it as spent the
| first time it is used, then every use after that will be
| denied.
|
| A card can be cloned, and it will work, once, it means one
| could steal a ticket by walking by and using appropriate
| equipment (not just a Flipper Zero as it is too short ranged)
| and use it before the legitimate owner does. I don't think it
| is something to worry about for a single use subway ticket.
|
| To improve security for multi-use tickets, one could use
| rolling codes: every time a ticket is scanned and its UID
| validated, some code is read from the NFC memory and it has to
| match a sequence, the next code is then written back to memory
| and has to be provided next time, invalidating any clone.
| Tickets can still be stolen, but you can't beat the system
| unless you crack the server-side encryption.
|
| More valuable tickets like commuter passes can use a different
| system with a challenge-response scheme.
| akira2501 wrote:
| > If you want actual security, you have to go for a challenge-
| response scheme
|
| Sure you just have to accept that you're now vulnerable to
| Denial of Service attacks, or just DoS due to unrelated service
| infrastructure outages caused by things like backhoes.
|
| > much less orient them consistently for the bond process to
| work?!
|
| It's not all that consistent. They have a 3% failure rate. And
| you have to accept a unique map of "broken chips" with every
| single order you receive.
| johnklos wrote:
| "Tie die"
|
| Ha ha ha ha... Love it! Always informative and interesting :)
| stacktrust wrote:
| You can use these around the house or car for location-tap
| automation. Tap on NFC tag and mobile phone can trigger a custom
| shortcut for local action or SSH script to Linux SBC or micro PC.
| Response time is about one second. Even the iPhone SE2 has an NFC
| reader.
|
| For vision-impaired people, NFC tags can be attached to objects
| and the phone can read an audio description when the object is
| tapped against phone.
| ck45 wrote:
| This reminds me a bit of Nabaztags, or maybe the reverse. They
| would also read something that resembles NFC and could perform
| an action.
| Tijdreiziger wrote:
| Around that time, I recall there being a lot of hype around
| RFID tags. E.g. the Touchatag was just a bunch of RFID tags
| and a USB RFID reader, but marketed as a consumer product.
| This never really seems to have caught on, though.
|
| Nowadays, I suppose most consumers do have RFID tags (debit
| cards, transport cards, building keys, e-Passports), they
| just might not be aware of the underlying technology.
| cypherpunks01 wrote:
| 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 forced to the mat
| first thing in the morning.
|
| NFC Alarm Clock
| https://play.google.com/store/apps/details?id=com.nfcalarmcl...
| is a really great and simple Android alarm. Share if anyone has a
| good iOS recommendation.
| scrollaway wrote:
| > _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"?
| unholythree wrote:
| The noise maker (alarm) is still close to him.
| jeffreygoesto wrote:
| Fair. My mother used to put one of those old rattling alarm
| clocks with two bells on top into a metallic dish and
| placed that combo at the other end of the room. Similar
| concept.
| cypherpunks01 wrote:
| 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.
| exe34 wrote:
| I have one set up with guest WiFi credentials, and somehow it's
| still a novelty to my friends when they visit for the first
| time!
| hlandau wrote:
| The NFC chip I want still doesn't exist: a CPU and flash I can
| write a program for, directly, no VMs, no Java, without an NDA'd
| datasheet.
|
| These exist, but they're all behind NDAs and you're not allowed
| to have them. They're used for e.g. EMV.
| userbinator wrote:
| How about something like this:
|
| https://hackaday.com/2009/06/27/avr-rfid-tag/
| bsder wrote:
| Is there a problem with the TI NFC chips? They all seem to be
| purchasable and have available datasheets.
| Gibbon1 wrote:
| I saw an NFC chip that has 512 bytes of eeprom. Talks to a
| micro via I2C and has an interrupt that can be used to wake it
| up.
|
| I think it's a M24LR04E.
|
| Costs like $0.50.
|
| I think these could be useful for devices where you have a
| limited amount of data you want to read or transfer. Like why
| have bluetooth and all the crap that entails when all you want
| to do is configure a device once.
|
| Advantage of a separate IC is you can use it with whatever
| microcontroller development stack you have working.
| Nition wrote:
| How is a chip like this actually manufactured? Especially the
| analogue components area.
| kens wrote:
| It's manufactured pretty much the same as any other chip, using
| photolithography. Most of the analog components would be CMOS
| transistors, just larger. They might use a BiCMOS process with
| a few extra steps to make bipolar transistors. And there might
| be an extra step for the capacitors. But overall, the chip uses
| an old, simple manufacturing process, much easier than cutting-
| edge processors.
| rwmj wrote:
| The chip seems like it's almost _too_ small? I don 't even
| know how they would cut up the wafer and how they would pick
| each die and mount it in the paper card.
| kens wrote:
| They cut the wafer apart with a diamond blade, 20 um thick.
| Laser cutters can make thinner cuts, but they cost more.
| Die pick-and-place machines can manipulate even smaller
| dies at high speed:
| https://www.syagrussystems.com/dts-2-die-sorter
| Sytten wrote:
| They are going away soon (TM), the tech is cool but they are
| impractical. I will be happy to use my credit card or phone.
|
| Too many times I have been stuck in 15-20 minutes queues to buy
| those tickets and you cant refill them with an app... Plus south
| shore and north shore have they own system it's a mess.
| rendx wrote:
| I dread the privacy implications. No thanks.
| vhcr wrote:
| No need to worry about privacy, facial recognition already
| takes care of that.
| akira2501 wrote:
| Is that admissible as evidence?
| kccqzy wrote:
| It is theoretically possible to refill it with the phone. You
| either have a stored value card where the value is stored on
| the card and have the phone's NFC talk to it, or you store the
| value in a server that has an API to add value and have the
| reader at the subway deduct the value from the server.
| speed_spread wrote:
| You can refill them with the Chrono app since last March. No
| more queues. Can't do nothing about Laval and Longueuil though.
| ForHackernews wrote:
| > a per-chip price of nine cents
|
| That still seems expensive for a $3.75 metro fare.
|
| 2.4% of the cost of your ride is the chip in the ticket itself?
| Maybe it's worth it because it lets them eliminate mechanical
| ticket-reading and unify paper tickets with other NFC payment
| methods.
| chgs wrote:
| Mifare is what's been used in London's Oyster cards for 20 years
| (not the ultralight ones mind), and Hong Kong for even longer.
|
| However oyster really is in its way out for most uses.
| contactless and especially a phone is far more convenient for non
| season use, and far less wasteful.
| akpa1 wrote:
| I'm looking forwards to the day they somehow manage to link a
| National Railcard to a contactless bank card.
| bobthepanda wrote:
| I feel like the approach will probably be that railcards
| become digital wallet compatible.
| emmet wrote:
| I'll have aged out before they ever manage this. Been on the
| to-do list for years.
| chgs wrote:
| You'd have to have a national railcard first. The only
| railcards that exist are specific ones for specific groups.
| akpa1 wrote:
| National Railcard is the name that TfL uses to refer to all
| of those different types of card.
|
| https://tfl.gov.uk/fares/free-and-discounted-
| travel/national...
| randunel wrote:
| There's a noticeable delay between contactless cards and
| oysters. Some people I know prefer oyster cards simply because
| they open the gates faster, in spite of having to top them off
| all the time.
|
| I'm looking forward to not having to choose one trade-off over
| the other.
| MBCook wrote:
| The article says the chips are made on a 180 nm process and they
| come out about the size of a table salt grain.
|
| We're now down in the single digits for fabrication in
| nanometers, although I know that sort of just a name. This chip
| is so tiny already, if you were to fab it on a process like 7 nm
| I'm guessing it would be unworkably small. Too hard to cut, too
| hard to manipulate individual chips once you did manage to cut
| them.
|
| So here's my question: how small can we make a chip _in area_
| while still being able to cut them out and easily use them?
|
| It's obviously not a concern for the hundreds of square
| millimeters of a large processor, but I've never heard about the
| opposite end of the spectrum before.
| kens wrote:
| There are a few issues. First, you lose 20 um due to the saw
| cut between the dies. I saw an NXP patent that said this was
| wasting 30% of the die for their tiny chips. If you made the
| chips smaller, you'd be wasting even more. Another issue is
| that you need some area for the bond pads, so you can't make
| your chips arbitrarily small or they will be useless.
|
| Looking at a random die pick-and-place machine [1], it handles
| dies down to 0.2mm in either dimension. So you could handle
| smaller dies than mine with an off-the-shelf machine, but not a
| lot smaller.
|
| [1] The video of the die machine in action is pretty cool:
| https://www.syagrussystems.com/dts-2-die-sorter
| EncomLab wrote:
| Ken is a treasure - he's a walking encyclopedia of all things
| electronic!
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