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31 series - Cu interface protocols, UICC and USIM

31.110 - Not available in this release 21.111 - USIM and IC card requirements USAT security USIM USAT USAT interpreter Up to the UMTS specifications


The 31 series covers the UICC and the applications that run there.

The UICC stores information associated with the user and the network operator, such as phone books, authentication keys and operator-specific applications. It evolved from the GSM SIM card, but unlike in GSM, there's a clear distinction between the hardware (the UICC) and the applications that run there (such as the USIM).

The specifications can be divided into four broad areas:

  • USIM: This is an application that supports the ME's communications with the fixed network.
  • USAT: This is a set of commands and procedures, which allows the UICC to run other applications that are specific to the network operator, and to communicate with external applications and the ME's user interface.
  • USAT interpreter: This encodes the commands and responses in the USAT, and allows an external application to mimic the behaviour of an application within the UICC itself.
  • USAT security: These procedures secure the data, commands and responses that are exchanged between the UICC and an external application.

Many aspects of the UICC have been generalised as part of a parallel ETSI project, to define a smart card platform (SCP) that can be used by applications other than telecommunications. Because of this, some of the 31 series specifications just contain references and amendments to the corresponding ETSI SCP specifications. The relevant ETSI specifications are listed on the following pages, and can be downloaded here.


ETSIEuropean telecommunications standards institute
GSMGlobal system for mobile communications
MEMobile equipment
SCPSmart card platform
SIMSubscriber identity module
UICCUniversal integrated circuit card
USATUSIM application toolkit
USIMUniversal subscriber identity module
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