Two technical terms are fundamental to understanding how eSIM works in IoT devices: the eUICC (the hardware) and the eIM (the SGP.32 management entity). Both terms are frequently encountered but not always clearly distinguished.
eUICC – The Hardware
The eUICC (embedded Universal Integrated Circuit Card) is the physical eSIM chip soldered or embedded in the device. It is the secure element that stores operator SIM profiles, executes the profile management software (LPA for consumer eSIM, IPA for SGP.32 IoT eSIM), and maintains the cryptographic credentials that secure all profile operations.
The eUICC is common to all GSMA eSIM standards – SGP.22 consumer eSIM, SGP.02 M2M eSIM, and SGP.32 IoT eSIM all use an eUICC as the hardware SIM element. What differs is the software running on and around it, and the management architecture above it.
The authoritative technical reference for eUICC architecture, the eUICC specification family, and how the hardware is implemented across device types is euicc.co.uk.
eIM – The SGP.32 Management Entity
The eIM (eSIM IoT Manager) is the server-side management entity introduced in SGP.32. It replaces the M2M SM-SR (Subscription Manager Secure Routing) used in the legacy SGP.02 standard. The eIM is the entity that decides which operator profile should be on which device and when, coordinates with the SM-DP+ to deliver profiles, and instructs the device’s IPA (IoT Profile Assistant) to execute profile changes.
The key advantage of the eIM over the SM-SR is operator independence: the eIM can manage profiles from multiple operators without requiring bilateral technical integrations between them. An enterprise deploying eRedCap devices with SGP.32-capable eUICCs can manage their entire global fleet from a single eIM platform regardless of which operators those devices are connected to.
For the full SGP.32 specification including eIM architecture, see SGP.32 and the detailed reference at sgp32.co.uk.