History: from cardboard to a computer

1950 — cardboard. The businessman Frank McNamara forgot his wallet in a restaurant — and came up with Diners Club: a cardboard card that lets you eat now and pay later. Nothing electronic: a name and a number printed on cardboard.

CLUB · MEMBER CARDJ. SMITHNo. 1250 · valid to 12/51printed on cardboardBANK · CREDIT CARD4000 1234 56784000 1234 5678J SMITH 12/62J SMITH 12/62digits embossed — raisedsignaturethe back: the stripeBANK4000 1234 5678inside — a computer1950cardboard1959plastic, embossinglate 1960smagnetic stripe1979 →chip with a processor
The card over 30 years: cardboard with a printed number, plastic with embossed digits, a magnetic stripe on the back — and finally a chip: a small computer inside that keeps a secret.

1958–1959 — plastic. American Express and BankAmericard issue plastic cards. The number and the name on them are pressed out — that is embossing: the digits are raised, you can feel them with your finger.

Why the digits were embossed

There are no electronic terminals yet, and calling the bank for every purchase takes long. So the merchant puts the card into an imprinter (nicknamed the "knuckle-buster"), a slip with carbon paper on top, and runs the roller over it by hand. The raised digits press through the carbon — the number and the name are printed on the slip. The customer signs, and the slip goes to the bank by post. The only way to check a card on the spot was a paper list of stolen numbers that the bank mailed to shops.

An imprinter, cross-sectionslid by handslipcarboncardthe roller presses — the raised digits push through the carbonSALES SLIP4000 1234 5678J SMITH 12/62amount: 12.50cardholder signature
Why the digits were embossed: with no power and no connection, the seller put the card into the imprinter and rolled it over — the raised digits printed through the carbon onto the slip. The signed slip was then sent to the bank.

Today this is not needed. The terminal reads the chip, and the bank answers in a second — there is no reason to copy the number onto paper any more. Many banks already issue flat cards: the number is printed or laser-engraved, or even moved to the back or into the app. That is cheaper and safer: a raised number can be seen from afar.

But raised digits are still loved. An embossed card feels "real" and expensive — banks keep it for premium cards, and some people ask for one on purpose. Now and then an imprinter is still taken out as a fallback — at hotels, at fairs, when the connection is down. And for collectors an old card with an embossed number is the memory of a whole era of paper slips.

Late 1960s — the magnetic stripe. At IBM a strip of magnetic tape is stuck onto the card: now a machine reads the number. Convenient — and dangerous: the stripe is just as easy to read and write onto another card. The copy cannot be told from the original.

The stripe under a magnifier: regions magnetized one way or the otherN→S1S→N0N→S1N→S1S→N0S→N0N→S1S→N0N→S1N→S1S→N0N→S1bitsreada devicecopies the bitswrite= a copy,indistinguishable
The stripe holds plain bits, like a tape. They are easy to read and write to another card: the copy is no different from the original. That is why a computer that keeps a secret and never gives it away was put into the card.

1974 — a card with a chip. The French inventor Roland Moreno patents a card with a built-in microchip. The idea: let the card itself keep the secret and show it to no one.

1979 — a computer in a card. The company Bull releases the CP8 — a card with a Motorola processor, memory and a program inside. In the 1980s France moves its payphones and banks to such cards.

1990s — EMV. The banks agree on one standard: the card proves that it is genuine by answering a random challenge from the terminal with its secret key. An overheard answer is useless — next time the challenge is different.

2000s — contactless. The same computer gets an antenna: the card is tapped instead of inserted. Later it moves into phones and watches.

The eight contacts on a card were fixed by the ISO 7816 standard (1987): power, ground, reset, clock and one data wire; the other contacts are spare. That is exactly what we are going to build.