After entering in an Administrator name and password for the OS X Mavericks installer you see the following message:
"This copy of the Install OS X Mavericks application can't be verified. It may have been corrupted or tampered with during downloading."
This message can appear if the date and time aren't set correctly on your computer. Use these steps to check your date and time, then try installation again.
Check your Date & Time System Preference by following these steps:
- Quit the OS X Mavericks installer.
- Choose "System Preferences" from the Apple menu ().
- Click the "Date & Time" icon in the System Preferences window.
- Click the "Date & Time" tab in the System Preferences pane that appears.
- If the padlock in the lower left is locked, click it and enter an administrator name and password when prompted.
- Make sure the "Set date and time automatically" checkbox is selected and the appropriate region is chosen in the field to the right of the checkbox.
Alternatively, manually set the date and time to an accurate setting (for example, the date should be set later than Oct 1, 2013).
Re-open the Install OS X Mavericks app (located in the Applications folder) and proceed with installation.
If the message reappears after checking the computer's date and time, the OS X Mavericks installer has likely been corrupted or altered during downloading. Try re-downloading the installer from the App Store again with a different network connection or location.