demovirus

There is .torrent-files which consists of some files rather than one file. I've changed the names of files that this torrent include. After changing names, i loaded new torrent-file into client. But tracker said that torrent doesn't registered. I tried to do it with different torrents. Answer is the same. What is the reason for that? May be tracker stores hash-sums of torrent files? I want to know very much.