I believe you are wrong. Hash values are not unique for data of the same size. But, for the purposes of bittorrent, I am not certain how many hashes there are. Bittorrent data are sent as "parts" of "pieces" that form the file(s). What I am not certain of is whether the hash values are created for these "parts". However, there are only a limited number of hashes possible, ~35^16 (not too sure) for 16 byte hashes, while files are binary data that have ranges far greater than that for each "part", 2^(8*part_size_in_bytes). So if each part is 11 bytes, the range of unique hashes has been gone over twice already. If you have information on what I am not clear about, please do tell.
[edited by kras on 11.12.2004 08:56]