CoreESIM Profile Structure: File System & Data Elements
3 min read
The CoreESIM profile, hosted on an eUICC, represents a critical component for mobile network access, encapsulating all necessary subscriber and network configuration data. Its structure is meticulously defined by industry standards, primarily GSMA SGP.22 for remote provisioning and ETSI TS 102 221 for the underlying UICC file system. A profile is essentially an encrypted, signed data package that, once downloaded and enabled, transforms the generic eUICC into a functional subscriber identity module for a specific Mobile Network Operator (MNO). This modular design ensures interoperability, security, and efficient management of subscriber identities across diverse ecosystems.
eUICC File System Hierarchy and Profile Data Elements
The eUICC leverages a hierarchical file system, analogous to a traditional UICC, to organize application data. This structure begins with the Master File (MF), which serves as the root. Beneath the MF are Dedicated Files (DFs), acting as directories for specific applications or data sets. Within these DFs reside Elementary Files (EFs), which are the actual data containers holding individual parameters. For eSIM profiles, key DFs include DF_TELECOM (0x7F20), housing standard telecommunication applications, and specific DFs defined by GSMA SGP.22 for profile management and storage. These include DF_eUICC (0x7F66), which often contains eUICC-specific metadata and administrative information, and the actual DF_PROFILE (e.g., DF_PROFILE_1, DF_PROFILE_2) for each active operational profile instance. Each downloaded profile is stored within its own dedicated logical container, ensuring robust isolation and independent manageability.
Within an active CoreESIM profile's file system, numerous EFs store the critical data elements required for network authentication, service provisioning, and subscriber identification. These include, but are not limited to:
EF_IMSI(International Mobile Subscriber Identity): The primary subscriber identifier, crucial for network registration.EF_KIorEF_OPC/EF_OPc(Authentication Key/Operator Specific Configuration): Cryptographic keys vital for secure network authentication (e.g., 3GPP Authentication and Key Agreement, AKA, algorithm).EF_AD(Administrative Data): Contains eUICC and application-specific administrative information, including capabilities and status.EF_PLMNsel(Public Land Mobile Network Selector): A prioritized list of preferred PLMNs to guide network selection.EF_SPN(Service Provider Name): The textual name of the service provider, often displayed on the device.EF_MSISDN(Mobile Subscriber ISDN Number): The subscriber's phone number associated with the profile.EF_ACC(Access Control Class): Defines access rights to certain services or network domains.