dowloading a secure file

During an installation I need to download a file from the Internet. Till now now I use the following code

NSISdl::download /TIMEOUT=30000 [url]https://repo.smartjava.nl/downloads/readme.txt[/url] "$INSTDIR/readme.txt" 

But for downloading this file I have to give up a username/password combination. Is there a function/plugin available to pass this username/password combination?

Remco Ruijsenaars