Does the PortableApps Platform conduct any internal checks on the files it downloads?
I came across this forum post, https://portableapps.com/node/18388, about using the digital signature to check if a file has been downloaded correctly.
I will be travelling to a country that is known to seed incorrect files for known encryption products and browsers. i.e. If you try to download EFF's TOR, you will get a fake version of tor that will install malware instead. This is why there are PGP signatures on the website along with the downloaded files.