Hashing

• Hashing is a one-way cryptographic procedure that allows you to create a signature based on an input string or file. The result is different for every input, but you can't reverse a hash to produce the original information. Secure password systems use this method to authenticate users while not storing passwords in vulnerable plain-text databases, as you can simply hash the user’s input and compare it to the stored, hashed password to see if they match. Similarly, you can verify that two files are identical by comparing their hashes without sharing any identifying information about the files.
  
  

DHT

• The Distributed Hash Table system takes advantage of hashing by sharing the hash values of users’ torrents across a decentralized network. When you run a DHT-enabled BitTorrent client, it connects to one of a number of DHT servers, receiving a list of other users connected to the network. From there, the client connects directly to those users and begins passing requests to the wider swarm. Nodes on the network share the hashed values of any torrents currently active on their systems, without sharing any identifiable information about the contents of those torrents.
  
  

Magnet Downloading

• When you download a file using a magnet link instead of connecting to a central BitTorrent server, your client sends a request out across the DHT network, passing from user to user, containing the hash value of the target file. Once the request finds a user sharing that file, your client connects directly to him to begin the download, while simultaneously searching the network for more users for increased download speeds.
  
  

Advantages and Disadvantages

• The chief advantage of the magnet system lies in its decentralized nature, allowing you to connect directly with other users without the use of a central tracker that may malfunction or shut down unexpectedly. Magnet downloads are usually slow to start, however, because the system has to identify file sharers across a much wider network without a central connection. In addition, participating in the DHT network requires your client to trade a constant stream of data with other nodes in the network, which can reduce your available bandwidth slightly and occasionally stress or overwhelm older routers.