This article provides the Technical details for SIM cards.
A SIM (Subscriber Identity Module) card contains the following:
- A 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
- Two passwords: a personal identification number (PIN) for ordinary use and a Personal Unlocking Key (PUK) for PIN unlocking.
Modern SIM cards can contain up to 250 phonebook entries and 25 SMS whereas earlier models would store as few as 5 messages and 20 contacts.
ICCID: Each SIM is internationally identified by its integrated circuit card identifier (ICCID). ICCIDs are stored in the SIM cards and are also engraved or printed on the SIM card body.
IMSI: SIM cards are identified on their individual operator networks by a unique IMSI. Mobile operators connect mobile phone calls and communicate with their SIM cards using their IMSIs.
PIN: It is a numeric code used to unlock the phone and/or complete a call or data transmission. It must be entered each time you use the phone unless you disable it.
PUK: If the wrong PIN is typed in more than three times, either the SIM card, the device or both become locked. They can be reverted to their original unlocked state by entering a PUK, provided by the service operator through verification. If the wrong PUK is entered ten times in a row, the device will become permanently blocked and unrecoverable, requiring a new SIM card. Once you enter the PUK code, you must set a pin.