Tracker sites wanting to ensure that Azureus only obtains peers directly from the tracker itself (i.e. no DHT or peer exchange usage) should embed the key "private" with the value "1" inside the "info" dict of the .torrent file:
Azureus clients (as well as others), upon seeing this flag set, will disable any sort of external peer exchange for that torrent; meaning only peers given out by the tracker will be used, even if that tracker goes down, as it is normally today.
This new field will be ignored by other BT clients, so it does not break compatibility as long as they've properly implemented the BT spec. Also, this new field WILL change the torrent's infohash, which means that torrents made without the secure flag aren't compatible with torrents made with it. If you update all the torrents on your web site, you will have to ask users to re-download the torrent files in order to let them connect to your tracker.
The Azureus Team recommends only using this flag for new torrents, as it'll provide a smooth transition for your users.
If you choose to apply this flag to existing torrents, you need to keep in mind that the infohash WILL change and will require all users to re-download the .torrent files and re-check their partial completes
Another way to secure torrents is to add a private flag to the announce reply (private = 1, number bencode entry). This is done tracker-side and not require any torrent editing.
- Note: This method is NOT secure. The secure method is to enable it with a flag in the .torrent file (as removing or changing the flag will result in a different infohash (and as such, a separate swarm identifier).
- Manually adding the private flag with a text editor may corrupt the torrent.
- The Azureus, ABC newer than 3.1.0 (3.1.0's maker does NOT include this function) and BitComet integrated torrent makers and EAD's TorrentBuild support adding this flag to torrents as they are generated.
- EAD's Private Flag Adder supports adding this flag to existing torrents.
- A PHP script to add the private flag to a torrent is in development.