A subscriber identity module or subscriber identification module (SIM) is an integrated circuit that is intended to securely store the international mobile subscriber identity (IMSI) and the related key used to identify and authenticate subscribers on mobile telephony devices (such as mobile phones and computers). The SIM circuit is part of the function of a Universal Integrated Circuit Card (UICC) physical smart card, which is usually made of PVC with embedded contacts and semiconductors. “Sim cards” are designed to be transferrable between different mobile devices. The first UICC smart cards were the size of credit and bank cards; the development of physically smaller mobile devices prompted the development of smaller SIM cards where the size of the plastic carrier is reduced while the electrical contacts remain the same. A SIM card contains its unique serial number (ICCID), international mobile subscriber identity (IMSI), security authentication and ciphering information, temporary information related to the local network, a list of the services the user has access to and two passwords: a personal identification number (PIN) for ordinary use and a personal unblocking code (PUK) for PIN unlocking.