How Do SIM Cards Work ?


SIM stands for Subscriber identity module, it is a technology which allows the mobile company to identify which Mobile Phone you’re using. It is a very crucial step as SIM card acts as a secondary medium for transmission of data from the cell towers.


In this new era of technology where signals are blasted from cell towers, these signals need to know exactly where to sent the data. This is where the role of sim cards come-in , these cards although small, contain a very important 64-bit(8 bytes) number which serves as a unique identifier. Although it takes only 8 bytes , there are about 10 Quintilian of numbers that can be stored in this way, so this method should work no matter how many people sign in for Verizon or other mobile network. 



When you turn on your phone with the SIM card inserted, your phone will pass your SIM card ID number along with an authentication key also found on the SIM card to your cell phone network provider, your network providers job is to then generate a random number and uses the key to form a new authentication number. The random number is then sent back to your phone. 


The same method is done by your phone to generate the response number, if the two numbers  match then your provider will instantly recognize and connect your phone to the mobile network. These steps although huge, is done by computers and happens within a few seconds.Also these security steps will ensure that it is your SIM card that is connected not anyone else’s , as a particular SIM card can only generate a particular number.


Other than identifying information SIM cards can also store personal information and has a  maximum storage capacity of 1 MB , this is pretty enough for storing about 100-250 contacts.


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