SoftSIMs implement eSIM functionality in software and so presents a very low cost solution. This approach is very popular in Asia where it is considered essential to have a very low Bill of Materials ( BoM ). The implementation of a SoftSIM eSIM solution is proprietary as no standards bodies have got involved with this method yet.
The software that facilitates a profile download can execute in one of 3 ways:
- On the GSM modem processor ( e.g. the Qualcomm or MTK chip ) but does not use a silicon trust zone and so does not offer a very high level of security. The manufacturers of the GSM modem chips have released demonstration code that can be used for this.
- On the processor of the OEM device itself. Most of the large Chinese handset manufacturers ( such as Xiaomi and Huawei ) offer this kind of solution and refer to it as a ‘virtual SIM’ or ‘virtual roaming’ solution.
- In an STK applet on the SIM processor chip inside a conventional SIM Java-card. This is usually implemented by sending a message via USSD to a server requesting a profile download and then sending the IMSI/Ki pair via an encrypted SMS