In the digital age, the smartphone has become more than just a device for communication, but a key to bank accounts, personal correspondence and sensitive data, which is why protecting access to a SIM card is a critical step in setting up any device, including the popular Xiaomi and Redmi models. Setting a personal identification number (PIN) creates the first and most reliable barrier to attackers trying to access your phone number or move your SIM to another device.
Many users neglect this feature, relying solely on a pattern lock or fingerprint scanner to unlock the screen. However, it is worth noting that these methods only protect the interface of the MIUI or HyperOS operating system. If you remove the SIM card and paste it into another phone, all your SMS with confirmation codes from banks will be available without any passwords. PIN activation blocks the card itself, making it useless for outsiders without knowing the secret combination.
The procedure for installing protection on Xiaomi devices is simplified and built deep into the system security settings. You do not need to download third-party applications or have programming skills. In this guide, we will take a detailed look at each step, consider possible errors when entering code and answer questions that often arise from owners of smartphones of the Chinese brand.
Why you need protection SIM card on Xiaomi
The main function of a PIN is to authenticate the owner when the device is turned on or the communication module is removed, and when a request for code entry appears on the screen, the operating system does not even start to boot. This means that without the right combination of numbers, the phone will not be able to register with the operator’s network, and therefore will not be able to receive calls or phone calls. SMS-This is a critical level of protection in the event of a gadget being stolen.
Imagine if your smartphone was stolen. An attacker could try to quickly turn off the device so you can't track it by geolocation, or just pull out the SIM card and paste it into his phone. If the PIN isn't set, he'd instantly access all your messages, including one-time passwords from online banking and social media. The security setup turns your SIM card into a useless piece of plastic for anyone who doesn't know the secret.
⚠️ Note: Standard PINs are often listed on the plastic card that your SIM card was pasted on when you bought them, usually combinations like 0000, 1111 or 1234, but they are not worth relying on – they are easy to guess.
In addition, modern fraud schemes are often based on interception of confirmation codes, and once they have access to your number, criminals can try to restore access to your accounts on messengers or payment systems, blocking the SIM card at the hardware level is the foundation on which all digital security of the user is built.
- 🔒 Complete isolation of the room from unauthorized use in someone else's device.
- 🛡️ Protection of bank transactions requiring confirmation through SMS.
- 📵 Blocking the ability to make paid calls at your expense.
Preparation for password installation and search PUK-code
Before you go directly to the menu settings, you need to do a little preparatory work. PUK-This is a special unlock key that you'll need if you mistype your PIN three times. PUK-The SIM card will be permanently blocked, and it can be restored only in the cabin of the operator with a passport.
PUK-The code is usually printed on the same plastic card as the SIM card itself, which is an 8-digit number, and if the plastic base is lost, the code can be found in the personal account of the mobile operator on the official website or through support. Write this code in a safe place, but don’t keep it in the notes of the phone you plan to protect.
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Take a photo of a plastic card with PUK-code and send it to a secure messenger or save it to a cloud storage, access to which is not tied to the phone number.
Also, make sure your Xiaomi device has the latest firmware installed. Although the SIM card settings interface rarely changes, older versions of MIUI may have bugs that prevent you from saving new settings. Check the updates in Settings → About the phone.
Step-by-step: Enabling PIN request
The activation process on Xiaomi smartphones is unified and executed through the standard settings menu. The interface may vary slightly depending on the shell version (MIUI 12, 13, 14 or the new HyperOS), but the logic of actions remains unchanged.
First, unlock the device and find the Settings icon (cogs), and in the list you open, you need to find the connection section «SIM-maps and mobile networks" or simply "Mobile Network. If search is difficult, use the search bar at the top of the settings screen by typing in the request «SIM».
☑️ Algorithm of protection installation
After entering the SIM card management menu, you will see a list of active modules. Click on the desired map (for example, click on the map, SIM In the menu that opens, find the item “Protection” SIM-cards” or “Blocking SIM-The default switch is in the off position. Activate it.
If you've never changed the code, try the standard combinations: 0000, 1111, 1234 or 12345678. The exact standard code for your operator is often listed on the operator's website or on the package. After successfully entering the old code, the system will ask you to come up with a new one.
| Action. | Description | Importance |
|---|---|---|
| Entrance to settings | Opening menu SIM-maps and mobile networks | Tall. |
| Entering old code | Use of standard code (0000/1234) | Critical |
| Change of code | Installation of a new combination of 4-8 digits | Tall. |
| Confirmation | Re-entering new code for verification | Medium |
Come up with a combination that's easy to remember but hard to guess. Avoid obvious birth dates or sequences like 1234. Once you type in the new code, it'll need to be re-corroborated, and then the protection will be activated, and the next time you restart the phone, the system will require you to enter the set combination.
How to change the PIN code to a new one
If you're already using security, but you want to change the code to a more convenient or complex one (for example, after buying a used phone or for prevention purposes), the change procedure is similar to the initial installation. You don't need to turn off the function, you just need to initiate the change process.
Same menu: “Protection” SIM-maps where you previously enabled lock, select the option “Change” PIN-code (or “Replace” PIN»). The system will first ask you to enter the current code, which is a security measure that prevents a password from being changed by an unauthorized person who has access to the unlocked screen.
Once the current password is confirmed, two fields will open: to enter the new code and to confirm it. The new PIN must consist of 4-8 digits. Note that letters and special characters in SIM PIN codes are not usually used. Type the new combination twice and press OK.
⚠️ Note: If you forget a new PIN code immediately after the change, you can only restore it through the new PIN code. PUK-Do not install a code that you may forget in 5 minutes.
Successful code change is confirmed by the system notification, and from now on, a new combination will be requested each time the device is turned on, and the old code will cease to act instantly.
What to do when blocking and requesting PUK
The SIM card security system is designed to give the user only three attempts to enter the correct PIN, so if you make a mistake three times, the card will be locked and a request will appear on the screen. PUK-This isn't a phone breakdown, it's a regular password protection.
To unlock, you will need to enter an 8-digit PUK-code that you had to find on a plastic card or in the operator's office, after you typed in the correct card. PUK-The system will immediately prompt you to set a new PIN. Enter the desired combination twice.
What happens if you exhaust PUK attempts?
It's important to enter PUK-The code is carefully, without haste. The errors are critical. If you can't find the code, go to the operator's website or call support from another phone. PUK through USSD-chatbots.
- 🔢 Carefully enter 8 digits PUK-code.
- 🔄 Immediately after you unlock, set a new PIN.
- 📞 Use another phone to contact the operator if the SIM card is blocked.
Features of working with two SIM cards
Xiaomi smartphones are famous for their support for two SIM cards, which is the standard for many users. When setting up security, it is important to understand that the PIN codes for the first and second cards are independent parameters. They may be the same for convenience, but are set and changed separately.
When you turn on a phone with two secure cards, the system will ask for the code sequentially, first for SIM 1, then for SIM 2 (or vice versa, depending on the priority set in the settings), if one of the cards does not have a PIN, the request will not follow.
You can manage each card separately in the settings menu, you can turn on the main card for calls, but leave the second card (used only for the Internet) without a password if download speed is important when the device is turned on. However, from a cybersecurity perspective, it is recommended to protect both slots.
It’s also worth noting that when you extract one of the cards hot (if the phone supports this feature without rebooting), the next time you insert or restart, the system will again request the code for that particular slot, which provides the flexibility of access control.
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SIM card protection does not affect the speed of the phone, but adds a few seconds to the start time of the device, requiring mandatory user intervention.
Frequent problems and ways to solve them
Users may experience a situation where the phone does not accept the code entered, although it seems correct, often because the keyboard activates the mode of typing instead of numbers, or the layout is turned on for another country. Make sure you enter the numbers.
Another common problem is software conflict: After the MIUI update, the security settings may go off or stop saving, in which case, try first to turn off the protection (by entering the current code), restart the phone, and then turn it on again.
If the phone writes "Network error" or "No network" after entering the correct code, check if the SIM card is installed correctly in the tray. Contacts may have oxidized or shifted. Wipe the contacts of the card with soft cloth and install it again.