The USIM card is the third generation mobile phone card, called the Global Subscriber Identity Module, and it is an integral part of the UMTS 3G network. The USIM card can not only do simple authentication function, but it has been proved that it is gradually transitioning to the mobile commerce platform and even the final multi-application platform. It is no longer difficult to realize other applications such as electronic wallet, electronic credit card and electronic bill on mobile phone.
In addition to supporting a variety of applications, the USIM card has also upgraded its algorithm in terms of security, adding the card's authentication function to the network. The PIN code refers to the password of the USIM card, which exists in the USIM card and the factory value is 1234 or 0000.
After activating the PIN code, you must enter the PIN code every time you turn on the computer and log on to the network. PUK code is a master key to unlock PIN code, with 8 digits in total.
Users don't know the PUK code, and only the staff in the business hall can operate it.
When the PIN code is entered incorrectly for three consecutive times, the USIM card will be locked automatically, and it can only be unlocked by entering PUK.
PUK code has 10 input opportunities. Therefore, at this time, users should never touch the PUK password by themselves. After inputting 10 times incorrectly, the USIM card will automatically start the self-destruction program, making the USIM card invalid. At this point, only go to the business hall to change the card.