Deep dive into eUICC Premium Industrial SIMs

To the naked eye, there isn’t much difference between consumer and IoT/M2M SIMs. The SIM in your mobile phone looks pretty much like the SIM in an IoT device, but there are critical differences. Your phone SIM is a commercial UICC plug-in, while an IoT device that is enabled to remotely manage subscriptions and has space for a removeable SIM is using an eUICC plug-in SIM. So, while they may look the same, the capabilities of eUICC SIMs are revolutionary for the IoT market- and the most secure eUICC formfactor on the IoT market today is the embedded SIM.

Let’s look at the different layers of an eUICC SIM and how those layers need to match in order for the SIM to work.

How are the layers linked together?

The hardware Operating System (OS) and electrical profile work like a minicomputer, with the different layers needing to be compatible for the SIM to function correctly. Not just any OS with work with any hardware, though, and it’s the hardware and OS compatability that decides if a SIM can support eUICC functionality.

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eUICC functionality allows the SIM to remotely download, switch, and enable a different profile.

This means there is no need to physically change the SIM – you can switch between different profiles in the same MNO, or from one MNO profile to a different MNO profile.

The Operating System

In addition to matching with the hardware, the OS supports important features on the SIM. If there is a PIN active on the SIM, the PIN handling is in the OS, as are authentication, access, and management of files and data, along with loading and deleting applications. Encryption/decryption and tamper proof functions are also handled in the OS.

One eUICC profile, many MNO profiles

An eUICC SIM has one eUICC profile but can store multiple MNO profiles, although only one MNO profile will be enabled at a time. So, what are these profiles?

The Tele2 (MNO) profile and eUICC profile are personalizations of the SIM. They contain network keys and subscription identifiers (IMSI, ICCID, authentications keys.) The Tele2 profile can either be personalized when the SIM is produced in the factory, or it can be downloaded later through SM-DP (Data Preparation)/SM-SR (Secure Routing).

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Profiles can also contain applets, which are small programs on the SIM dedicated to fulfilling a particular task.

The task could be implementing the business logic to change a connectivity profile based on rules, such as when one network is not available and you want the next best available one.

If the SIM has a local applet, this is stored in the Tele2/MNO profile. If it’s a global profile it will be in the eUICC profile. To provide interoperability applets are typically developed in JAVA.

Today Tele2 IoT has an applet that clears forbidden networks, and in 2024 local management and management of 5G stand-alone on eUICC will be launched.

What is unique in an eUICC SIM?

Every eUICC SIM has an EID (eUICC identifier) which is the administrational key in the hardware layer. If there is an MNO profile change the SIM will have a different ICCID and IMSI, but once the eUICC SIM is produced its EID is never changed.

The EID contains 32 digits compared to the ICCID’s 20. There is a shortened version of the EID printed on both the embedded and plug in eUICC chip. The EID is provisioned in the SM-SR, which is also responsible for managing the status of profiles on the eUICC.

Hardware and formfactors

When using a SIM that has eUICC capabilities it is important that the hardware is robust and long lasting. ETSI has a classification of the different environmental properties in which the SIM is graded.

On a SIM technical sheet, the environmental performance can be represented in a string, together with which version of ETSI specification was used. The string of letters can then be looked up to understand what the SIM can withstand.

For example, the environmental property temperature has the grades TS, TA, TB, and TC. The Premium industrial SIM is graded as TB in its ETSI, string while a commercial SIM is graded TS. The eUICC Premium Industrial SIM can be stored and operational in the temperature range of -40 °C to + 105 °C ,while the UICC commercial SIM can only be used in the temperature range of -25 °C to + 85 °C

As mentioned before there are two types of SIM cards: plug-in formfactors (2FF, 3FF, 4FF) that are removable, and embedded formfactors that are soldered into the device. The most popular embedded SIM on the IoT market is the MFF2 (M2M Form Factor).

As the abbreviation applies the MFF2 SIM is designed for M2M/IoT use cases and is delivered on what looks like an old film reel. It is one of the most secure chips due to being soldered into the device and the device can be designed in a way that makes it more robust in general. An embedded SIM is also a greener alternative to plug-in SIMs, with less plastic and metal per SIM.

If you would like to know more about our SIMs and eUICC functionality, please feel free to reach out to the Tele2 IoT team.

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