 cases of SIM and USIM interaction are defined in 3GPP TR 31.900. The SIM/USIM contains information specific to a subscriber, such as its telephone number, unique identification number including Mobile Station International ISDN number (MSISDN) and IMSI (International Mobile Subscriber Identity), and home system identification information. The first UICC/SIM card was made in 1991, with Munich smart card maker Giesecke & Devrient selling the first 300 cards to Finnish wireless network operator Elisa Oyj (formerly Radiolinja) [4]. Table 10.3 shows the key differences between traditional and high capacity UICC cards. Once the SIM card has been activated, it can also be managed remotely via an OTA (Over the Air) platform, whose functions include remotely updating card profile, downloading application, deleting applets on the cards, and SO on. This also enables the introduction of new services during deployment or post-issuance [19]. Smart Wireless Devices Table 10.3 Low and high capacity UICC cards Attributes Traditional UICC High Capacity UICC Operating System Native (vendor specific) Java Card Memory 64-128 KB (EEPROM) Frequency 5-15 MHz 10-50 MHz Processor 8- or 16-bit processor 32-bit processor Capacity 250 contacts 2000 contacts Silicon 150 nm 100 nm 85 X 54 mm 25 X 15 mm 10.5.3.1 SIM/USIM Application Toolkit SIM Application Toolkit (commonly referred to as STK) is a standard of the GSM system which enables the SIM to initiate actions which can be used for various value-added services. STK is defined in the GSM 11.14 standard in 1995 for GSM networks. USIM Application Toolkit (USAT) is the equivalent of STK for 3G networks. USAT enables the USIM to initiate actions which can be used for various value-added services delivered over mobile devices. USAT takes advantage of the multi application environment of 3G devices by not activating until a specific application has been selected, unlike STK which is activated at startup. USAT is defined in standard 3GPP 31.111 for 3G. From Release 4 onwards, GSM 11.14 is replac