The Pirate Bay announced today that it was killing its popular BitTorrent tracker, relying instead on the truly decentralized DHT protocol to handle file location and downloading. For TPB, it's all about removing centralized points of control.
The Pirate Bay's BitTorrent tracker is down for good—but that's by design.
The Pirate Bay has been intermittently unavailable for last few months as copyright holders have pressured its various ISPs to cut off service to the site in the wake of Swedish court decisions against the site's operators. Even though BitTorrent is a peer-to-peer network, it relies on .torrent files that are typically hosted on trackers—and The Pirate Bay's tracker was one of the largest. When the site was down, the tracker was compromised, and the crew behind the Bay decided that the system relied too much on a single point of failure.
Today The Pirate Bay announced on its blog that the tracker will remain down indefinitely. The site's other primary function, indexing, will remain available, but will now rely on a distributed peer-to-peer hash system that does not need centralized trackers.
"Now that the decentralized system for finding peers is so well developed," said the post, "TPB has decided that there is no need to run a tracker anymore, so it will remain down! It's the end of an era, but the era is no longer up2date. We have put a server in a museum already, and now the tracking can be put there as well."
In place of tracking comes distributed hash tables (DHT), which have been implemented for years by most leading BitTorrent clients. Instead of obtaining .torrent files from a central repository, DHT is able to locate files simply by querying other peers in the BitTorrent swarm. This results in more network overhead and processor power, and it can also cause issues for certain routers—but it also removes a central point of control.
It also allows The Pirate Bay to better make the argument, which it tried in court earlier this year, that it is really just a search engine for .torrent files—like a specialized Google. One objection to this argument was that TPB actually ran its own tracker and therefore helped to facilitate the actual downloads.
To connect the browsable index on its website to the content in question, The Pirate Bay now offers "magnet links" for most of its content. Rather than pointing to a .torrent file hosted at some tracker, magnet links simply contain a hash of the file in question. This hash is passed along to the BitTorrent client, which can then use DHT to find BitTorrent peers who have the file available for download.
For instance, here is an example magnet link:
magnet:?xt=urn:btih:6bd956b1844ee643f51856d636e da1cbbe9a9fcc&dn=The.Big.Bang.Theory.S03E08.The.Adhesive.Duck. Deficiency.HDTV.Xvi
It's a fairly simple setup, as you can see. The magnet link begins with an exact topic (xt), which provides the file's hash value using BTIH (BitTorrent Info Hash); the client can then use this hash to search the swarm for this exact file.
This magnet link also includes a display name (dn), which can be used by the client to show users, in human-readable form, what they are downloading.
According to The Pirate Bay, "This is the future. And the present."
Source: ars technica