No I'm not. It has nothing to do with whether the hashing algorithm is "fixed" or not, it has to do with what you're hashing. The thing being hashed (accordin

No I'm not. It has nothing to do with whether the hashing algorithm is "fixed" or not, it has to do with what you're hashing. The thing being hashed (according to BEP0003) is the bencoded form of the info value from the metainfo file. What's the "info" value? Why it's a list of dictionaries that (are also bencoded) contain: * pathnames for each file * the length of each file * a list of hashes for each chunk of each file * whatever else you want: the thing is extensible. If you can introduce whatever you want, you can start with something valid, and introduce invalid chunks until it collides. If you can do this, you can force a collision for around £150k and a month[2]. [1]: http://www.bittorrent.org/beps/bep_0003.html http://www.bittorrent.org/beps/bep_0003.html [2]: https://sites.google.com/site/itstheshappening/ https://sites.google.com/site/itstheshappening/