User Configuration > Administrative Templates > Microsoft Office 2016 > Security Settings
User
HKCU\software\policies\microsoft\office\16.0\common\security
This policy setting enables you to specify an encryption type for password-protected Office 97-2003 files.
If you enable this policy setting, you can specify the type of encryption that Office applications will use to encrypt password-protected files in the older Office 97-2003 file formats. 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: