I have the following tracker request:
"info_hash=%92%c345%c0%28%15%e4rr%b1y%17%b7%cbs%0a%ef%9a%fc&peer_id=-UT2210-%2abP%b2%c23~NaN7-%7c%0f%1f&port=56541&uploaded=0&downloaded=0&left=461680&corrupt=0&key=6AD19369&event=started&numwant=200&compact=1&no_peer_id=1"
and I would like to decode the info_hash and peer_id fields in JavaScript.
I've tried the unescape(), decodeURI() and decodeURIComponent() functions but they didn't return the expected results.
The info hash present in the HTTP GET Request to the Tracker can be decoded as follows:
If there's a '%' character, then the next 2 characters are a part of the original 40 char SHA-1 hash.
so, you can break the encoded info_hash as follows:
%92 %c3 4 5 %c0 %28 %15 %e4 r r %b1 y %17 %b7 %cb s %0a %ef %9a %fc
All the 2 char groups prefixed with the '%' symbol belong to the original hash.
Now, for the remaining characters. We need to find the corresponding Hex value of them. You can use asciitable for reference.
For instance, 4 in base 10 is 34 in hex.
Combining all together this way we get:
92c33435c02815e47272b17917b7cb730aef9afc -> SHA-1 hash of the torrent file.
The peer_id will give us information about the client name and version. In this case:
-UT2210-%2abP%b2%c23~NaN7-%7c%0f%1f
This is in Azureus format.
UT corresponds to µTorrent and 2210 gives us the version.
The process of decoding can be automated using a Perl Script easily.