Currently mobile service is distributed on a plastic SIM card that must be purchased and inserted into a device. As SIM cards are becoming smaller and now require a tool to replace them in a device this is inherently more expensive, less reliable and problematic. Whereas most other ‘digital’ services can be purchased online and downloaded ( or streamed ) to a device. Examples of this are music, movies and eBooks. The connected car is being designed with inbuilt eSIMs.
On this site, the word ‘eSIM’ will be used to describe any mechanism used to facilitate an IMSI/Profile download. There are basically 3 main kinds of eSIM:
- eSIMs that comply with standards developed by the GSM Association ( GSMA ). These offer a very high level of security and are accepted by most of the tier 1 MNOs. They derive their level of security by relying on a physical device, a chip which is commonly called an Embedded Universal Integrated Circuit Card ( or eUICC ). These are currently more common in Europe and North America.
- Devices that incorporate software that provides the same functionality of a physical SIM chip. These offer less security than a physical eUICC, but provide a lower cost Bill of Materials. These are very popular in Asia and are commonly referred to as SoftSIMs. Each SoftSIM implementation tends to be proprietary.
- In Asia also it is popular to have programmable SIM cards. The IMSI identity inside these is usually changed by sending information Over the Air ( OTA ) to the SIM. This can be done using an STK Applet on the SIM or directly to the EF file within the SIM. These SIMs are sometimes referred to as ‘OTA SIMs’.
- System on a Chip ( SoC ) devices that integrate the eSIM functionality inside an SoC device such as a GSM modem processor chip. They are a cross between an eUICC and a SoftSIM in that the eSIM functionality is implemented in a silicon ‘trusted zone’ inside the processor. These are currently being developed and there is no standard for this.