Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Japan's IC cards are weird and wonderful

aruarian.dance

Post reply on HN
Print view View original

101–110 of 302 posts

Re: Japan's IC cards are weird and wonderful

#101

Post by lxgr »

raluk wrote: post #85

One problem with fast writing is that it requres more energy to transmit from reader to a card in order for a card that has no internal source of power, to toggle bits. It is harder compared to just reading a bit from a card. Additonaly it is tricky to implement trasaction with single write, given that data transfer can be interrupted (for example user removes card from RF field). I am not sure if single write is eno…

> One problem with fast writing is that it requres more energy to transmit from reader to a card in order for a card that has no internal source of power, to toggle bits.

Contactless cards manage to boot up a JVM and run bytecode with the energy provided by the field, and many also run RSA with fairly large keys. I doubt that toggling some bits in an EEPROM factors in too much.

> I am not sure if single write is enough for making this robust/transactional.

Transactions are usually implemented via some form of two-phase commit, I believe, to support what's called "tear resistance". If the transaction is incomplete, the reader tells you and you just tap the same card at the same gate again.

Not sure about the implementation, but the feature is supported by all contactless stored-value cards I'm aware of.

Re: Japan's IC cards are weird and wonderful

#103

Post by lxgr »

numpad0 wrote: post #43
TheChaplain wrote: post #14

I love IC cards. They had them on all transport where I live, but a few years ago they changed to QR codes.. Now it's a fiddle with an app, then try to get the right angle on a smudgy reader. Getting onboard takes much longer and it feels like technology sent us 2 steps back instead of forward. IC cards are better, and if they could be integrated in the phone then it would be even better and faster for everyone.

It's about fees and control. Whether it's EMV(Europay Mastercard Visa) or JR East, they take 3% commission on every single sales + realtime sales data for your competitors to abuse. So alternative choices gets occasionally chosen to replace them, I think often as bargaining chips and a backup plan.

OP is talking about QR codes, not EMV open-loop systems.

Re: Japan's IC cards are weird and wonderful

#104

Post by lxgr »

0xCMP wrote: post #29
TheChaplain wrote: post #14

I love IC cards. They had them on all transport where I live, but a few years ago they changed to QR codes.. Now it's a fiddle with an app, then try to get the right angle on a smudgy reader. Getting onboard takes much longer and it feels like technology sent us 2 steps back instead of forward. IC cards are better, and if they could be integrated in the phone then it would be even better and faster for everyone.

iOS supports ICs fine. It has supported Suica since 2017 when I used it instead of the physical card. Forcing use of an app and QR codes does seem like a significant step back, although I guess it makes paper tickets much easier to implement with the same scanner.

Android, however, does not support them at all unfortunately (at least on phones not targeted to the Japanese market).

Re: Japan's IC cards are weird and wonderful

#105

Post by AshamedCaptain »

aikinai wrote: post #95
AshamedCaptain wrote: post #55

I don't understand -- we are talking about 100ms or so of latency? which is almost completely dwarfed by any mechanical action such as the gates actually opening?? This is about as ridiculous as it gets. The videos that compare the UK system with the JP system practically show the same throughput, even when in the UK video most people are using magnetic/paper tickets (which by necessity are going to be much slower th…

The comparison video is kind of pointless since they're both at very slow times. If you see a Tokyo gate at rush hour with people packed wall-to-wall but moving quickly, that's what the latency was optimized for. And as others have mentioned, it's two things, speed and distance. FeliCa triggers both faster and farther away. And it never errors; you just made up that assumption. Also in Japan no one walks up to the ga…

What you are describing is exactly all the problems with gates. Having them open-by-default improves somewhat. Having 100ms less reading time improves nothing. You are still limited by the speed of everyone else (cultural aspects are irrelevant as they are not improved by reader tech). If you want to improve entry throughput, have _no gate at all_ so that people do not have to bottleneck there. If you really have to put a validator, put it elsewhere.

Re: Japan's IC cards are weird and wonderful

#106

Post by lxgr »

PaulHoule wrote: post #2

If I had to ask “why is it so fast?” I’d turn it around and ask “Why are western systems so slow?” and posit that Western capital has an ideology that throughout matters by latency doesn’t. (As Fred Brooks puts it, “Nine women can have a baby in one month”). As an individual or a customer you perceive latency directly though, and throughout secondarily. So it comes down to empathy or lack thereof.

Indeed. But the primary problem with western transit gates/turnstiles is this:

Japanese IC transaction: Less than 100 ms.

EMV IC transaction: Hundreds of milliseconds.

The person in front of you in the New York subway only realizing that they might have to look for their phone or card in their bag as they're already blocking one of very few turnstiles, and your train is arriving: Timeless.

Re: Japan's IC cards are weird and wonderful

#107

Post by secabeen »

PaulHoule wrote: post #4
aecsocket wrote: post #3

Earlier quoted context omitted.

The magnitude to which FeliCa was faster shocked me as well when I found out. But it's not like the latency is insignificant: it's obvious how much faster people can get through a Tokyo metro gate than a London one. So clearly it must have some kind of financial impact as well, if an entire city's public transport system works slower because of it. Even ignoring empathy for a second, isn't this the kind of thing that…

It is not just capital but the interpersonal and bureaucratic factors. Technically the way to think about latency is that a process has N serial steps and you can (a) reduce N, (b) run some of those serial steps in parallel, and (c) speed up the steps. For one thing, different aspects of the organization own the N steps. You might have one step that is difficult to improve because of organizational issues and then th…

> meanwhile they are paying the flight crew to wait

Most flight attendant and pilot union contracts only pay them based on the hours with the door closed or in flight. (This is changing, but it's how it's been for a long time.) This reduces the incentives for quick boarding, as most of the flight crew is not being paid for that time.

Re: Japan's IC cards are weird and wonderful

#108

Post by mrb »

"what makes Japan's transit card system (IC cards) so unique compared to the West"

Actually other western transit system cards are similar to Japan's. For example in Paris the transit passes (Navigo cards) are stored-value systems and hold a record of the last few scans (three I think). You can also read them with any NFC smartphone and see what's stored inside. The tap at the entrance of a transit vehicle is near instant as the reader doesn't need to interact with a backend since everything is stored on the card itself.

Re: Japan's IC cards are weird and wonderful

#109

Post by AshamedCaptain »

lxgr wrote: post #87
AshamedCaptain wrote: post #55

I don't understand -- we are talking about 100ms or so of latency? which is almost completely dwarfed by any mechanical action such as the gates actually opening?? This is about as ridiculous as it gets. The videos that compare the UK system with the JP system practically show the same throughput, even when in the UK video most people are using magnetic/paper tickets (which by necessity are going to be much slower th…

> If you really want to speed how people go through the gates, then _remove the damn gates_. That comes with other problems. Transit gates have the big advantage of providing you with instant feedback on whether your ticket or mode of payment is valid or not. I've seen tourists get in trouble with ticket inspectors at least once in a very unpleasant way for simply having pressed the wrong button at an inscrutable tic…

> Transit gates have the big advantage of providing you with instant feedback on whether your ticket or mode of payment is valid or not.

So do the validators that are put in waiting areas, inside the trains, etc. in cities with no gates. That you can literally use at the time you want to use them (waiting for the train, inside the train, etc. ) , rather than forcing a bottleneck to everyone.

> As others have already said, Japanese gates are open by default

And this by itself already makes more of a latency difference than the entire IC card system does. Imagine what removing the gates altogether does.

Re: Japan's IC cards are weird and wonderful

#110

Post by lxgr »

chgs wrote: post #8

I haven’t noticed any delay in london with a card, phone might be 200ms slower than credit catd. I Haven’t been to japan for a decade, are they really that much faster - and does it make a difference? What happens if a card is wrong/doesn’t scan/is invalid/etc at the higher speed?

The speed difference isn't in not phone vs. credit card, it's credit card vs. stored value card.

Stored value cards are optimized for speed and cost, and as a result have shared symmetric keys available in both card and reader. That enables extremely fast transactions.

EMV cards are (also) optimized (at least in the offline case, which transit gates use – the latency to talk to the bank backend would be too high) for security. The security model doesn't trust readers to keep keys secret, which means you need asymmetric cryptography for card authentication. The specs are old, which means RSA – which is very slow to run in cheap ICs embedded in these cards produced at scale.

Post reply on HN