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Making Smart Cards Wise

At first, that mainly means equipping new phones with what is known as a “contactless IC” chip. Smaller and thinner than a dime, and attached to an antenna made from a thin film and embedded in the phone, the chip is like a small, fast, rather stupid computer, one that is exuberantly cheap to manufacture. The chip chosen by DoCoMo is Sony’s FeliCa (the name comes from “felicity” and “card”), which has nine kilobytes of random-access memory and just enough smarts in its onboard programming to respond to the short-range radio signal beamed out by a chip reader/writer.

In Tokyo, the most familiar example of a reader is at the turnstile used in Japan Rail train and subway stations. From station vending machines, passengers buy “smart cards”-plastic rectangles the size and shape of a credit card with chips inside. Each card is “charged” with a predetermined sum: approximately $10, $30, or $50. People stick the cards inside their wallets and purses and slap them on the turnstile as they pass through. In the brief interval when the card brushes by the turnstile, the chip inside the card and the reader inside the turnstile perform a “cryptographic handshake”-that is, they exchange a set of encrypted messages. The turnstile tells the card its location; the card tells the turnstile how much money it contains; the turnstile deducts the base cost of a ticket. On the way out, the exit turnstile performs an analogous transaction, calculating the actual cost of the journey and deducting it from the card.

The entire transaction takes less than a tenth of a second. Not only does that help shuttle people quickly through the turnstiles, a key consideration for Japan Rail, but it also means the exchange of data takes place before users can pull away their cards. That reduces the risk of incomplete transactions-a major technical challenge in systems where cards do not physically pass through readers. According to Tadashi Morita, FeliCa’s chief engineer at Sony (no relation to Sony’s late founder, Akio Morita), slower systems run the risk that users will send payment information but walk past the readers before they have received their tickets in return. “They don’t know if they’ve been charged or not,” he says. “You don’t want [people] to pay twice, or not at all.”

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