SIM card (first commercial SIM)

What it is

A SIM, or subscriber identity module, is a small chip card that identifies a mobile subscriber to the network and stores the keys used to authenticate them. The first commercial SIM was delivered in 1991 by Giesecke+Devrient of Munich to the Finnish GSM operator Radiolinja, today Elisa, as the GSM digital network went live.

How it works

The SIM holds a microcontroller with secure memory. When a phone joins the network, the operator sends a random challenge; the SIM combines it with a secret key that never leaves the chip and returns the answer. Because the key stays inside the card, the subscription can move between handsets while the identity stays protected. The same idea now runs in software form in the eSIM, which operators provision remotely to a chip soldered into the device.

Why it stands out

• It applied the smart card principle, patented in Germany by Jürgen Dethloff and Helmut Gröttrup at the end of the 1960s, to mobile phones.
• Gröttrup had earlier been a guidance specialist on the V-2 rocket and led German engineers in the Soviet missile programme before returning to West Germany in 1953.
• France's Roland Moreno filed his own smart card patent in 1974 and is often called the card's inventor; the German applications came several years earlier, while Moreno's PIN-based design did much to make cards practical.
• G+D says it activated its 100 millionth eSIM in 2023.

Where you meet it

In almost every mobile phone, and increasingly in cars, smart meters and connected machines, either as a plastic card or as an embedded eSIM. The card format has shrunk several times, from credit card size to the nano SIM, but the secure chip principle is unchanged since 1991. In 1998 G+D also launched what it describes as the world's first SIM-based mobile banking application. G+D has also supplied payment cards, health insurance cards from 1993, and banknotes for 145 central banks.

Sources

• G+D: The SIM turns 30
• DPMA: Die Chipkarte
• heise online: The development of the smart card
• Wikipedia: Helmut Gröttrup