Can LibreOffice/UNO programmatically add passwords to existing .docx/.xlsx/.pptx files?

TL;DR version - I need to programmatically add a password to .docx/.xlsx/.pptx files using LibreOffice and it doesn’t work, and no errors are reported back either, my request to add a password is simply ignored, and a password-less version of the same file is saved.

I’m trying to script the ability to password-protect existing .docx/.xlsx/.pptx files using LibreOffice.
I’m using 64-bit LibreOffice which is the latest version at the time of writing, on Windows 8.1 64-bit Professional.
Whilst I can do this manually via the UI - specifically, I open the “plain” document, do “Save As” and then tick “Save with Password”, and enter the password in there, I cannot get this to work via any kind of automation. I’m been trying via Python/Uno, but to no gain. Although the code below correctly opens and saves the document, my attempt to add a password is completely ignored. Curiously, the file size shrinks from 12kb to 9kb when I do this.

Here is my code:

import socket
import uno
import sys
localContext = uno.getComponentContext()
resolver = localContext.ServiceManager.createInstanceWithContext("", localContext)
ctx = resolver.resolve( "uno:socket,host=localhost,port=2002;urp;StarOffice.ComponentContext" )
smgr = ctx.ServiceManager
desktop = smgr.createInstanceWithContext( "",ctx)

from import PropertyValue

oDocB = desktop.loadComponentFromURL ("file:///C:/Docs/PlainDoc.docx","_blank",0, tuple(properties) )

sp1.Value='MS Word 2007 XML'


I’ve had great results using Python/Uno to open password-protected files, but I cannot get it to protect a previously unprotected document. I’ve tried enabling the macro recorder and recording my actions - it recorded the following LibreOffice BASIC code:

sub SaveDoc
rem ----------------------------------------------------------------------
rem define variables
dim document   as object
dim dispatcher as object
rem ----------------------------------------------------------------------
rem get access to the document
document   = ThisComponent.CurrentController.Frame
dispatcher = createUnoService("")

rem ----------------------------------------------------------------------
dim args1(2) as new
args1(0).Name = "URL"
args1(0).Value = "file:///C:/Docs/PasswordDoc.docx"
args1(1).Name = "FilterName"
args1(1).Value = "MS Word 2007 XML"
args1(2).Name = "EncryptionData"
args1(2).Value = Array(Array("OOXPassword","secret"))

dispatcher.executeDispatch(document, ".uno:SaveAs", "", 0, args1())

end sub

Even when I try to run that, it…saves an unprotected document, with no password encryption. I’ve even tried converting the macro above into the equivalent Python code, but to no avail either. I don’t get any errors, it simply doesn’t protect the document.

Does anyone have any solution? Do you have some LibreOffice code that can do this (password-protect .docx/.xlsx/.pptx files)? Or OpenOffice for that matter, I’m not precious about which package I use. Or something else entirely!

Cross-posted to stackoverflow, and got a correct answer there.