Magnet URI Scheme - Use of Content Hashes

Use of Content Hashes

The most common use of Magnet URIs is to point to a particular file based on a hash of its contents, producing a unique identifier for the file, similar to an ISBN or catalog number. Unlike traditional identifiers, however, content-based signatures can be generated by anyone who already has the file, without the need for a central authority to issue them. This makes them popular for use as "guaranteed" search terms within the file sharing community where anyone can distribute a Magnet link to ensure that the resource retrieved by that link is the one intended, regardless of how it is retrieved. While it is theoretically possible for two files to have the same hash value (known as a "hash collision"), cryptographic hash functions are designed to reduce that occurrence to a practical impossibility – even if an expert with vast computational resources is intentionally looking for two files with the same hash value.

Another advantage of Magnet URIs is their open nature and platform independence: the same Magnet link can be used to download a resource from numerous applications on almost any operating system. Because they are concise and plain-text, users can copy-and-paste them into e-mails or instant messages, a property not found in, for example, BitTorrent files.