hack0r.net

I finally managed to get this project far enough to publish a first alpha version.
The idea is to utilize browsers to do filesharing. Well I didn’t develope this idea in the first place, but I picked it up at ha.ckers.org.

The architecture is rather similar to the one from bittorrent. I initially wanted to implement the bittorrent protocol, but I couldn’t find a plain, comprehensive description of the bittorrent protocol. After developing it, I guess it would have been next to impossible to implement a protocol that is suited for a pure p2p based environment.
So like in bittorrent BrowserShare has a server, like a tracker, that only stores where to reach the client and the hash of the file he desires and/or is willing to share.
Then there are clients, they are the ones where the data originates from or ends at. Like .torrent files in bittorrent the client needs .bash files to be able to share it with others or get it from others.
Last but not least there are the browser instances that help to share the content. They get a list of users from the tracker and search for parts one has and others not. After having found a match the browser downloads the part from the client who shares it and sends it to all users needing it. Thereby sharing his bandwith with those who probably don’t have so much bandwidth.
This makes it very easy for someone who wants to help the community sharing files, but doesn’t want to install some kind of software. All he has to do is to point his browser to a special URL and he is a bandwidth sharer.

I’ve made a very short and plain presentation for our open study group CInsects, which describes the protocol and the used features a bit. You can find the slides here.

The next steps in this project are developing a GUI, making it possible to create .bash files from directories and prohibiting malicious usage of the browsers. The third point is the most difficult, because in the current setup the browser includes JavaScript from the clients, which can be arbitrary. A solution to this problem can be a crossdomain XMLHttpRequest, but this feature isn’t yet implemented in most stable branches of the commonly used browsers, as far as I know.
But nevertheless one could just test if this feature is available and choose this safer way to transmit information, leaving the current implementation as a fallback.
The current JavaScript could also be improved regarding this problem. The browser page the JavaScript code relies on could be refreshed after a given timeout to have a new, clean instance of the JavaScript. I’m not too well informed about browser caching, but it should be possible to get the browser to save all pages that transported data to him, so it won’t need to fetch it again from the clients.
Also the search algorithm to find matches in who needs parts and who serves them is currently very simple. It only searches for the first match and then just takes it. A more sophisticated solution would be to find the shareable part with the most needing users, combined with some random picking. The random picking is needed, because of two reasons.
The first is that, if there are several browsers sharing bandwidth and all are relying on the same algorithm to find the part they want to share next, they will all download the same part from probably the same client and then provide them to the other clients. Thereby they waste a huge amount of bandwidth by doing the same thing in parallel.
The second is, if there are constantly new clients joining, desiring the same file, and there are only very few nodes that just need one last part of another file, that is shareable, they would possibly never get their last part.

You can check it out via svn at https://hack0r.net/browserShare with username and password both anonymous. I don’t know if it will work on windows machines, it’s only been tested on linux. I tried to not introduce platform dependent code, but I didn’t test it, so I don’t know. The usage is descibed in the README. You should probably update your version frequently, as there is a pretty long todo list and I hope to go about them soon.

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