User Configuration > Administrative Templates > Microsoft Word 2016 > Word Options > Security > Cryptography
User
HKCU\software\policies\microsoft\office\16.0\word\security\crypto
This policy setting allows you to specify the number of bytes of salt that should be used. If you enable this policy setting, the bytes specified will be used. If you disable or do not configure this policy setting, the default length of 16 will be used.