karajorma, parity files are used on irc where files are split up into small chunks, then scattered over different fora to be reassembled later. Torrents contain the entire file in one place so that strategy isn't needed.
In fact I've never seen one torrent that used them, not that they couldn't---they're simply a complication of usenet life.
It's almost unheard of for someone to download a broken torrent. Most people would not download a torrent that had no seeders or leechers.
If I make parity files, he'll have to download some pieces again from somewhere, I'm not sure how that would work.
jr2, a 99% match is fine. Anyway, whatever you use to make the torrent is going to hash the file, not a Power Toy.