(Note that this really has nothing to do with the original post, just clarifying something for the hell of it) Err >.> Checksums can be the same, reguardless of how big they are, its just extremely rare outside of CRC16/32 to find the exact same checksum. A checksum is just a number, for the sake of not going into giant numbers lets start with CRC32. A CRC32 checksum takes up 4 bytes, 0xFFFFFFFF. That is simply a number, its max value is 4,294,967,295. That means that if you line up 4,294,967,295 files plus 1 extra file, then atleast 2 files will have the same checksum. This is true no matter how many bytes the checksum contains, once the maximum value is reached, then any additional files will make the checksum useless to some extent. SHA-1, the checksum that BitTorrent uses can go upto 2048 bytes as far as I know, however BitTorrent only uses 20 byte checksums.