The signature verification error in the brush machine indicates that the current firmware is not the latest firmware of Apple, and the problem can be solved by using the latest firmware to brush the machine again. Brush: 1, turn off the iphone, connect the computer with the data cable, and open the iTunes software of the computer. 2. Press and hold the power button for 2 seconds. 3. Press and hold the Home key 10 second to force the shutdown without releasing the power key. 4. Press the power button 1 time without releasing the home button. Press and hold the Home button for about 15 seconds, and the information of connecting Itunes icon will be displayed on the screen of the mobile phone to enter DFU mode. 5. The computer has voice and SMS prompts to discover new hardware, and iTunes prompts that there is an iphone that needs to be restored. Click Restore, and itunes will automatically download the latest firmware to update and refresh.