What is a bit torrent info hash?
Answer:
Each torrent has a unique fingerprint called a "hash" or "info hash".
This info hash is used to ensure that the completed download of the content associated with a torrent will be uncorrupted.
The content in a torrent is broken down into pieces, or "bits", for transfer.
Each piece has its own hash and its hash is compared to the info hash of the torrent.
If the hashes match, then the piece is accepted as part of the download.
If the hashes do not match, then the piece is rejected.
The info hash ensures that the completed download will be uncorrupted and also ensures that malware can not be injected into an otherwise clean torrent.