User Configuration > Administrative Templates > Microsoft Office 2016 > Security Settings > Escrow Certificates
User
HKCU\software\policies\microsoft\office\16.0\common\security\crypto\escrowcerts
This policy setting allows you to specify a certificate to use as an escrow key for password protected files. If you enable this policy setting, the certificate you specify is used as an escrow key for all password protected files that are created on this machine. If you disable or do not configure this policy setting, an escrow key is not configured.