There will always be more networks.
Even if everyone has this installed, WinZip defeats any possible attempt to compare the file with any non-zipped (with the same encryption key) file.
Just zip it up with a key, stick the key in the file name. Voila, no comparing. Once the database caches a copy of the zipped version, just re-zip it with a different key.
Simple and cheap. Unlike the software they're trying to write.