what is SHSH?
the full name of p>SHSH is Signature HaSH blobs, which is also called "signature certificate". A certificate used to verify the legitimacy of iTunes when it resumes firmware operation.
when using iTuens to upgrade/restore the firmware, iTunes will submit the ECID to Apple's verification server and apply for the SHSH to upgrade or restore the firmware of this system version. Apple will send a SHSH certificate corresponding to the ECID to iTunes through the verification server, and iTunes can continue to upgrade or restore the firmware of this version corresponding to this SHSH.
Simply put, SHSH is equivalent to a key, and it needs to match the corresponding SHSH when swiping an iOS version.
Precautions
1. You can obtain the currently available upgraded version by querying SHSH, and all Apple's open verified iOS versions and devices can support it (at present, Apple has officially turned off the verification of iOS 11.4 and below, and cannot downgrade to iOS 11.4 and below).
2. Make sure that the device does not turn on the function of finding my iPhone activation lock, or determine the Apple ID and password of the current device login, otherwise the device may not be activated after the brushing is completed.
3. Make a backup of important data before refreshing, or check "Refresh with User Data" to prevent important data from being lost. If downgrading operation is performed, it is not recommended to check "Save User Data to Brush Machine", which may lead to brush machine failure or equipment abnormality. Can be classified and backed up by AISI assistant, and then operated. After successful brushing, the data can be classified and recovered.
The interface of "Professional Brush" introduces
How to downgrade the p>iPhone X? | AISI Assistant Professional Brush Tutorial
Query SHSH: You can get the information of iOS version that can be brushed by querying SHSH.
import firmware: import the firmware of the system version that needs to be refreshed.
brush now: after importing the firmware, you need to click "brush now" to brush.
activate immediately: activate the equipment after the brushing is completed.
keep user data to refresh: you can check when refreshing iOS 7 and above, and the device data will not be lost after refreshing, and the device does not need to be activated.
Keep the baseband from being upgraded: only valid for "iPhone 4 downgrading or swiping iOS 7 or below". Moreover, it is meaningful to keep the baseband only for devices with network locks. If the current device does not have network locks, it doesn't matter whether the baseband is kept or not.
Operation steps of "Professional Brush"
1. Connect the mobile phone with the AISI assistant on the PC side, click "Brush Prison Break"-"Professional Brush", and first select "Query SHSH" from the options on the right side of the current interface to obtain the system version that can be brushed into the current device.
how to downgrade p>iPhone X? | AISI Assistant Professional Brush Tutorial
2. Enter DFU mode according to the prompt;
before p>iPhone 7/7P, the model enters DFU mode: keep pressing the Home button of the device, then press the power button of the device until the screen of the device goes out, release the power button of the device after 4 seconds, but keep pressing the Home button until the software prompts "success", and then release the Home button. (For iPhone 7/7P, please use the "volume down button" instead of the Home button);
how to enter DFU mode for iphone 8/8p/x model: press the volume up key and volume down key once quickly, then keep pressing the power button, wait for the device to shut down by itself, press the volume down key for 5 seconds, and release the power button but do not release the volume down key until the software prompts "success".
how to downgrade p>iPhone X? | AISI Assistant Professional Brush Tutorial
3. After entering DFU mode, SHSH will be automatically queried to get the information of the brush version, with red indicating the version that cannot be brushed at present and yellow indicating the system version that can be brushed.
how to downgrade p>iPhone X? | AISI Assistant Professional Brush Tutorial
4. After confirming the printable version of the current device, download the corresponding firmware at the "Firmware Download", and the download progress and storage location can be viewed in the "Download Center";
how to downgrade p>iPhone X? | AISI Assistant Professional Brush Tutorial
5. Wait for the firmware download to be completed, return to the Professional Brush interface, click "Select Firmware", and select the downloaded firmware (if you can't determine the path, go to the Download Center in the upper right corner to open the file location search);
how to downgrade p>iPhone X? | AISI Assistant Professional Brush Tutorial
6. After selecting the firmware, click "Brush Now". If it is not currently in DFU mode, you need to enter DFU mode first (refer to the tutorial method in step 2), and the brush will be automatically performed after entering DFU mode;
how to downgrade p>iPhone X? | AISI Assistant Professional Brush Tutorial
7. Wait for the brush to be completed, as shown in the figure below, indicating that the brush is completed (the process takes about 1 minutes);
how to downgrade p>iPhone X? | AISI Assistant Professional Brush Tutorial
8. Wait for the phone to start and turn on, and click "Activate Now" (if you save the data, you don't need to activate it), as shown in the figure, indicating that the activation is complete.