GoKawiilIf you’ve ever ridden a train in Japan, there’s a good chance you’ve held a Suica card in your hand and tapped it against a station gate.
Even though it was developed back in the 90s, Suica’s technology is really impressive even by today’s standards. Every time you tap it, a complex transaction happens in the fraction of a second, without needing a battery or live internet connection.
It’s easy to take IC transit cards for granted now that they’re part of everyday life, but let’s not forget how much work went into engineering them several decades ago before cashless or contactless payments were common.
Here’s a breakdown of how these cards work, and the surprisingly bumpy story of how they came to be.
How the cards actually work
Every Suica card has a chip storing two things: a unique card ID, and your current balance. Both of those live on the card itself, rather than a central server.
When you tap your card on a terminal, it reads and rewrites the card locally in an instant, with the entire transaction processed in under 200 milliseconds. For each tap, the card and terminal mutually authenticate each other and generate a fresh encryption key to prevent spoofing.
The cards have no battery and aren’t self-powered in any way. Instead, the reader on the gate emits an electromagnetic field that powers the card just long enough to complete the transaction.
Why not sync with a central server each time? The reason is simply that it would take too long.
With the sheer volume of people passing through Tokyo’s stations each day, calling a server would be extremely risky. Transactions would take longer, causing people to slow down at the already-crowded station gates. And any network issues like latency, packet loss, or server downtime would cause the gates to shut down, which would be disastrous during peak commuting hours.
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