title: How are Hash Trees useful?
body: <p>I was reading on Wikipedia about <a href="https://en.wikipedia.org/wiki/Hash_tree">hash trees</a>, and I don't understand the benefits or purposes of this structure - they seem to require more hashes than just one per leaf with no significant use of the extra hashes.</p>
  
  <p>For example, the use case on wikipedia is that they are used to validate data received in a P2P system. But why is this better than having a one-to-one mapping of blocks numbers and their hashes, without having the tree structure?</p>
  
  <p>Could someone please explain how and why hash trees are useful?</p>
  
  <p>Thanks in advance,</p>
  
  <p>Moshe</p>