User Configuration > Administrative Templates > Microsoft Office 2016 > Security Settings
User
HKCU\software\policies\microsoft\office\16.0\common\security
This policy setting allows you to specify an encryption type for Office Open XML files.
If you enable this policy setting, you can specify the type of encryption that Office applications use to encrypt password-protected files in the Office Open XML file formats used by Excel, PowerPoint, and Word. The chosen encryption type must have a corresponding cryptographic service provider (CSP) installed on the computer that encrypts the file. See the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Cryptography\Defaults\Provider\ registry key for a list of CSPs installed on the local computer. Specify the encryption type to use by entering it in the provided text box in the following form: