Wireshark-users: [Wireshark-users] BitTorrent info_hash decoder using Wireshark

From: firstname lastname <psykosonik_frequenz@xxxxxxxxx>
Date: Tue, 8 Nov 2011 12:51:07 -0800 (PST)
I have a pcap file which has traffic captured between the client and the server. Here, the server is a tracker and it looks like an announcement message from a Torrent client to the Tracker requesting to download a file.

The request looks like below:

GET http://tracker21.df6d4cf3-2787-4001-80ff-e8a23e7ff1ec.automated.snxd.com/?info_hash=%FEg%F6mth%90%5E%84%F6%F5z%E3%E8%DFu%E7%FA%14%0E&peer_id=<>&port=0&uploaded=0&downloaded=0&left=3760800 ......

The info hash looks like this: %FEg%F6mth%90%5E%84%F6%F5z%E3%E8%DFu%E7%FA%14%0E

I want to decode this info_hash. I believe wireshark has the capability to dissect the Bittorrent Protocol, however I am unsure of whether there is a way to make it decode the info_hash and peer_id fields as well?

I have searched on Google for algorithm used to encode the info hash but not much success.

http://nakkaya.com/2009/12/03/bittorrent-tracker-protocol/

This is one reference, but I am trying to understand the algorithm. While doing that, I got this thought.

It would be great if we can get the info_hash, since this way we can conclude which file was being downloaded from the tracker.

Regards,
NeonFlash