Amazon Hot Sales Prepaid Scratch Mobile Phone Card

SIM card is the subscriber identification card of digital cellular mobile phone. Its full name is "subscriber identification module". In the GSM digital mobile phone system, the SIM card plays an extremely important role. It is not only an important part of the mobile phone, but also an identity card for every GSM mobile phone user. Therefore, the SIM card realizes the concept of recognizing people and not recognizing machines.

Specifically, its functions mainly reflect the following aspects. The data stored by SIM card can be divided into four categories: the first category is fixed data. This type of data is written by the SIM card center before the mobile phone is sold, including the International Mobile Subscriber Identification Number (IMSI), authentication key (KI), authentication and encryption algorithm, etc.