Xiaomi’s Inadmissible Signature: What is the Mistake and How to Fix It

Faced with an "Inappropriate Signature" message on your Xiaomi, Redmi or POCO screen? This is one of the most common problems when trying to update firmware, install custom software, or even after resetting, it blocks access to the system, making the device virtually useless. But don't panic: 90% of the time, the error can be fixed without going to the service center.

In this article, we will go into detail what “unacceptable signature” means, why it appears on Xiaomi devices (including Mi 11, Redmi Note 10, POCO X3 and others), and provide step-by-step instructions to fix the problem, paying special attention to secure methods that will not lead to data loss or “bricking” of the gadget.

Important: If you see this error after a failed firmware or unlocking the bootloader, don't try to re-flash the device without understanding the reasons. This can make things worse. Next, only proven solutions from Xiaomi experts and users.

What does the “Unacceptable Signature” error mean?

The message “Invalid signature” (or “Unacceptable signature” in Russian) indicates a problem with the digital signature of the firmware. In Xiaomi devices, each official and custom firmware has a unique electronic signature that is checked by the bootloader before installation. If the signature does not match the expected or is corrupted, the system blocks the download to prevent the installation of potentially dangerous software.

This error can occur in several scenarios:

• 🔄 When you try to update the firmware through Settings → The phone. → Updating the system.
• 📱 After resetting to factory settings (Wipe Data in Recovery Mode).
• 🔧 When installing custom firmware (such as LineageOS or Pixel Experience) TWRP.
• 🔒 After unlocking the bootloader (bootloader unlock) with the Mi Unlock Tool.

In most cases, the problem is due to incompatibility of the firmware and bootloader versions, corruption of update files, or the use of inappropriate regional software (for example, trying to install Global ROM on a device with China ROM).

The main reasons for the error

To effectively fix a problem, you need to understand the root of it. TOP-5 Why Xiaomi Issues “Inadmissible Signature»:

1. Incompatibility between the firmware and the bootloader. For example, you're trying to install Android 13 on a device with an Android 12 bootloader. This is a typical error when you manually update via fastboot.
2. Damaged firmware files: A downloaded archive from the software may not be fully downloaded or modified (e.g. when editing build.prop).
3. Install EU ROM on a device with China ROM (or vice versa) without first unlocking the bootloader.
4. Anti-Rollback: Xiaomi blocks rollbacks to older firmware versions if they are below the current version of the Anti-Rollback Index.

Critical moment: on devices with MediaTek processors (for example, Redmi) 9A, POCO M3) The error "unauthorized signature" is often associated with blocking the preloader partition. SP Flash Tool and Xiaomi Authorized Account to Unblock.

How to check the current version of the firmware and bootloader

Before you start fixing the error, you need to know the current firmware version and the status of the bootloader, which will help you choose the right recovery method.

If the device is at least partially loaded (reaching the Mi or Redmi logo), follow the following steps:

1. Press Volume Up + Power to log into Fastboot Mode.
2. Connect your phone to your PC and open the command prompt (cmd in Windows or Terminal in macOS/Linux).
3. Enter the command: fastboot getvar all Look for the strings version-bootloader and version-baseband.
4. To check the firmware version, type in: fastboot getvar product and compare the result with the official versions on the Miui Downloads website.

If the device does not respond to buttons, try a hardware reset:

• 🔌 Turn off the phone from charging.
• 🔄 Hold the Loud up. + Power for 10-15 seconds.
• 📱 If you have a Recovery menu, select Reboot to Bootloader.

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If the fastboot getvar all command doesn't work, try first entering fastboot devices to make sure the device is PC-defined. If necessary, install the Mi Flash Tool drivers.

How to eliminate the error "Inadmissible signature"

Depending on the cause of the error, there are different methods of correcting it, and the following are step-by-step instructions from the safest to the riskier (but more effective) method.

Method 1: Install official firmware via Mi Flash Tool

This is the most reliable way if the error occurred after a failed update or reset.

• 💻 Windows computer (7/10/11).
• 🔌 Cable USB (preferably original).
• 📥 Official firmware for your model (download from the official website).
• 🛠 Mi Flash Tool Tool.

Step-by-step:

1. Unpack the downloaded firmware (file with the extension.tgz or.zip) in a folder without Cyrillic characters.
2. Install the Mi Flash Tool and run it on behalf of the administrator.
3. Connect your phone in Fastboot mode (clip Volume Down + Power).
4. In the Mi Flash Tool, click Select and specify the path to the unpacked firmware.
5. Select Clean All mode (if you want to save data – Clean all and lock, but this will not always work).
6. Press Flash and wait until it is completed (usually 5-10 minutes).

Important: If the Mi Flash Tool gives an error of 0x80070002 or 0x80070005, try running the program in Windows 7 compatibility mode or disable the antivirus.

Download the correct firmware version for your model|Install Xiaomi drivers (via Mi) PC Suite)|Disable antivirus and firewall|Charge your phone at least 50 times%|Connect the original USB-cable

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Method 2: Unlock the bootloader (if it is blocked)

If the error occurred after trying to install custom firmware, most likely the bootloader is blocked. Xiaomi requires official unlocking through the Mi Unlock Tool.The process takes up to 72 hours (due to account verification) and includes the following steps:

1. Link your device to your Mi Account in settings (Settings → Xiaomi Account).
2. Enable USB debugging (Settings → About Phone → MIUI Version → 7 times click on version → Return to Additional → For Developers → Debugging by USB).
3. Connect your phone to your PC, launch the Mi Unlock Tool and follow the instructions.
4. Once unlocked, re-install the firmware via Fastboot or TWRP.

⚠️ Warning: Unlocking the bootloader erases all data on the device, including photos and apps).

Method 3: Bypassing Anti-Rollback (for power users)

If the error is related to Anti-Rollback, you can try to bypass the protection with a modified firmware or patch. This method is only suitable for devices with an unlocked bootloader!

Option 1: Use the Anti-Rollback Remove patch

Option 2: Install firmware with an increased ARB index

⚠️ Warning: Incorrect anti-Rollback bypassing can cause the device to fail completely ("brick"). Use this method only if you are confident in your actions!

Frequent errors in correcting an “unacceptable signature”

Many users make the problem worse by trying to fix it in unproven ways, and here are the most common mistakes and their consequences:

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If after several attempts of firmware the device does not respond to buttons and is not determined by the PC, do not try to restore it yourself through EDL Mode.

Prevention: How to avoid mistakes in the future

To avoid having to deal with an “unauthorized signature,” follow these simple rules:

• 🔄 Update the firmware only through official channels (Settings) → System Update or Mi Flash Tool).
• 📥 Check the integrity of the downloaded files. Compare the hash amounts (MD5 or SHA-1) formal.
• 🌍 Don't mix firmware from different regions. ROM, Don't install China ROM needlessly.
• 🔒 Unlock the bootloader in advance if you plan custom firmware.The process takes up to 3 days.
• 📡 Keep an eye out for Anti-Rollback updates. Don't roll back on old firmware versions.

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Before updating, back up your important data via Settings → Additional → Backup and Reset or with Mi PC Suite. This will save your files even if something goes wrong.

FAQ: Answers to Frequent Questions