How eSIM works

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As often happens when a technology sits quietly for years until adopted by Apple, suddenly, it’s grabbing headlines. Almost three years ago, we wrote about the first smart watch that supported so-called [i]eSIM[/i] technology, but only now is it becoming widely known — because the iPhone XR, XS, and XS Max support the technology, allowing a virtual SIM to be added to a regular SIM card.

How does it work and what are the advantages? Let’s take a look.

SIM card evolution
The first mobile phones had no SIM cards. Instead, they were programmed by a carrier, with the “user account” for network identification stored in the device’s memory. SIM cards appeared in the GSM standard in 1991, allowing subscribers to use their phone on any network and their carrier account (that is, mobile number) with any phone, simply by inserting a piece of plastic with a microchip.

For as long as phones and modems were the only devices connected to the network, everyone was satisfied with this arrangement. The only thing that happened to SIM-cards as the years rolled by is that they became increasingly Lilliputian: the mini-SIM (the one we remember as “normal”) was replaced by the micro-SIM, and then the nano-SIM. But the limit has been reached; the nano-SIM is just a microchip with bond pads, without a single millimeter of excess plastic.

Now that the Internet of Things is here, with its sensors, smart watches, and other, even tinier devices, even a nano-SIM slot is an inadmissible luxury. Enter the eSIM, a built-in SIM card.

At first glance, it seems to mark a return to programmable phones. However, this evolutionary microchip (approximately 5×6 mm, a fraction of the size of a nano-SIM) not only stores subscription data, but also can be downloaded over the air, remotely. Practically speaking, that means no need to manually insert SIM cards into tens of thousands of parking sensors or street-light control modules, or reorder a whole batch of cards when changing operators.

Full reading: https://www.kaspersky.com/blog/how-esim-works/25431/