Blizzard Downloader
 

Hi, I hope I won't bring down the wrath of mods with this question, I figured I'd get the most qualified answers here.

I noticed how the blizzard downloader is able to "authorize" downloads and will deny downloads of their pre-release stuff to people who aren't authorized - they don't have a beta key for example. I know the downloader is built on top of bittorrent, I'm a software engineer working in bio-tech and I need to build a tool to share large files between authorized sites. If they managed to get this kind of functionality out of torrent without breaking the protocol, this would be the perfect tool for me, but I'm lost as to how they could've done that. Or are the privileged downloads using some sort of more secure fallback? I'd be eternally greatful for any insight you guys could give me on this.

I tried writing Blizzard tech support they told me to write directly to Blizzard by mail, I'm not sure how long that process takes.

They didn't build it "on top of" bit-torrent. They simply implemented the bit-torrent specification with the downloader and point it to a private, secure tracker that they run.

BitTorrentSpecification - TheoryOrg

If you need to distribute a large amount of data to multiple sites, then bit-torrent is definitely one way to efficiently do that...assuming the networks they all operate on play nice with bit-torrent traffic. Of course, most just cap your bandwidth per month these days unless you're a business. Then you just get charged extra if you go over your limit.

Can't you just use analyse the 'key' parameter (in which you could put an encoded value) of a tracker request and only send the peer list back when it has the correct value?

Sorry if that's a dumb question, just my first thought after a quick glance over the specification (and never having seen it before).

Definition of the parameter:
key: Optional. An additional identification that is not shared with any users. It is intended to allow a client to prove their identity should their IP address change.

Well if you want to take a closer look at the topic, there is a tool, called WoWTorrentEx that can extract the .torrent from the Blizzard Downloader, but yes, I am pretty sure they work with keys, like most private trackers do, you download a specifically keyed .torrent which authorizes you against the tracker to download exactly the files linked to that .torrent file.

http://capnbry.net/wow/downloads/WoWTorrentEx-4.zip