I got a mobile flower card, saying that my parents are self-sufficient, and I will activate it. Can I not let them activate themselves?

Telephone cards are SIM cards, also known as subscriber identity cards and smart cards. GSM digital mobile phone can only use this card. Phone cards can store short message data and phone numbers, and can be used to identify customers in GSM network. When talking, the voice information of customers uses SIM card, which completely prevents parallel lines and phones from being eavesdropped.

SIM card is called "subscriber identification card", which is actually a smart card with large-scale integrated circuit, and is used to register important data and information of users. One of the most important functions of SIM card is authentication and encryption. When a user moves to a new area to make or receive a call, the switch must authenticate the user to determine whether it is a legitimate user.

At this time, both SIM card and switch use authentication algorithm to calculate authentication key and 8-bit random number. If the calculation results are the same, the SIM card is identified, otherwise the SIM card is rejected and the user cannot make a call. SIM card can also use encryption algorithm to encrypt voice to prevent eavesdropping.

Specifically, its functions are mainly reflected in the following aspects. The data stored in the SIM card can be divided into four categories. The first category is fixed data, which is written by the SIM card center before the mobile phone is sold, including International Mobile Subscriber Identification Number (IMSI), authentication key (KI), authentication and encryption algorithm, etc. The second category is temporarily stored network data.