Uploaded Photos Wtih Sim Card Size Is Frozen
A Subscriber Identity Module (SIM) card is a chip inside most modern cellular phones that stores information your telephone needs to communicate with your carrier'due south prison cell towers. SIM cards come in different sizes and if you were to remove the SIM card from your phone y'all wouldn't be able to text, phone call, or access annihilation on the internet.
What Is A SIM Menu?
Believe it or not, SIM cards accept been on the scene since 1991. They were first developed by a German language manufacturer for a Finnish mobile carrier. Billions of SIM cards accept been sold to date.
SIM cards are mandatory for phones connecting to the Global Organization for Mobile communications (GSM) networks, which is the telecommunications standard in over 193 countries that stores identification and security information on the card.
A SIM card is a small smart bill of fare made up of embedded contacts and semiconductors that has gone through four sizes over the years:
- Full-Size (1FF or 1st Form Factor) was the size of a credit card; 85.6 mm x 53.98 mm.
- Mini-SIM (2FF) was drastically smaller coming in at 25 mm x 15 mm start being used in 1996.
- Micro-SIM (3FF) made improvements in length with measurements of 15 mm x 12 mm.
- Nano-SIM (4FF) is the most recent form and is 12.3 mm x 8.eight mm.
Equally phones got smaller and thinner, the need for smaller components inside became more apparent. Having a card the size of a credit card inside a device the same size wasn't realistic. Nowadays, SIM cards accept been stripped downward, removing almost all the surrounding plastic, and are essentially just a small chip.
The adjacent-generation SIM technology is chosen an Embedded-SIM (eSIM). Information technology's a non-replaceable chip soldered straight to your device's circuit lath and contains something chosen "Remote SIM Provisioning," which allows customers to remotely activate the east-SIM on their devices. Right now, Google'south Pixel 2 and the Apple Scout 3 (forth with some cars), are the only real consumer tech using eSIMs, just that'southward expected to change quickly.
What's Stored On A SIM Bill of fare?
A SIM card stores an International Mobile Subscriber Identity (IMSI) number, which is a unique 15 digit number identifying the card on carrier's mobile network. The IMSI is an important part of the lookup process and determines the network to which a mobile device connects.
Along with the IMSI, a 128-flake value authentication key (Ki) is sent to verify your SIM with the GSM cellular network. The Ki is assigned past the operator and stored in a database on their network.
A SIM menu is likewise capable of storing SMS messages and the names and phone numbers of up to 500 contacts, depending on the memory size of the SIM bill of fare you lot have. If yous have to change phones for whatsoever reason, you're able to transfer your contacts via the SIM card painlessly.
Most SIM cards contain between 64-128 KB of storage.
How Does A SIM Work?
Essentially, a SIM card serves as your phone'due south credentials to access the carrier network. Because the SIM holds this data, you're able to pop it into any telephone with the same carrier, or an unlocked phone, to access the network.
Here's how it works:
- When you lot boot upwardly your device, it obtains the IMSI from the SIM, and so relays the IMSI to the network in society to request admission.
- The operator network searches the database for your IMSI and the associated Ki.
- Bold your IMSI and Ki are verified, the operator then generates a random number, signs it with your Ki using the GSM cryptography algorithm for computing SRES_2, and creates a new unique number.
- The network then sends that unique number back to the device, which then passes it to the SIM to use in the same algorithm, creating a 3rd number. This number is then relayed dorsum to the network.
- If both numbers match, the SIM card is deemed legitimate and is granted admission to the network.
So if you pause the screen on your phone, while information technology's getting fixed you tin can accept your SIM out and put it in a replacement phone and however admission phone calls, texts, and data from your network.
RELATED: How to Unlock Your Cell Telephone (And so You Can Bring Information technology to a New Carrier)
Security
Then, what if your phone gets stolen? Can someone just pop out your SIM card and stick it into some other phone?
Well, yeah.
Someone could put that card into some other phone, and and then use information technology to make calls, which tin can get quite expensive if it's used to make premium calls. If your SIM too contains contact or other information, they volition take access to that as well. The skillful news is that most modernistic phones do non store that kind of information on SIM cards.
Still, the first thing y'all should do if your telephone or SIM carte du jour is stolen is report the theft to your carrier. They can then block that SIM card from being used at all.
You can too protect your SIM bill of fare with its own Pivot using the "SIM Lock" feature on your phone. The characteristic locks the SIM card with a PIN and then that the menu can't exist used without unlocking information technology. Even though you set the characteristic using your phone, the Pin is tied to the SIM card itself. Both Android and iPhone take this feature in the respected settings menu.
With and so many SIM cards being actively used, they may just be the most used security token in the world. With your phone number existence the key to two-factor authentication, hackers are e'er trying to figure out ways to get hold of your phone number so they tin accept control of your email, social media business relationship, and even your bank account. To do this, they apply a method chosen "SIM swapping," which allows them to take over anything tied to your number. By calling your mobile provider and pretending to exist you, they play tricks the representative into sending a new SIM carte to them, gaining consummate control.
How do you gainsay this technique? With another PIN, of class. This fourth dimension, you just telephone call your carrier and enquire them to add together a security Pivot to your account. That style, everyone who talks to them to make account changes (including you) must provide the Pin number first.
Image Credit: fortton/Shutterstock
Source: https://www.howtogeek.com/353634/what-is-a-sim-card/
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