[SOLVED] This copy of the Install macOS High Sierra.app application is damaged…
Most common cause of this error is due to the invalid time in your mac. All you have to do is correct it then retry the installation.
Step 1: Check whether you have the same issue. Open the terminal.
Step 2: Check the date and time using the date command.
Step 3: Update the date and time of your machine using the date command.