title: Generating Private, Unique, Secure URLs
body: <p>I'd like to generate a secure one-click-access type of url similar to the examples below. I'll be using PHP but that is irrelevant as I'm just looking to understand the underlying concept. Some answers suggest using a GUID, but I don't think that will give me an absolutely unique, secure URL like below.</p>
  
  <pre><code>#    Google Calendar
  3qq6jlu04ptlhmb9fencsu5t2k
  #    Private
  3qq6jlu04ptlhmb9fencsu5t2k
  #    Private 'token'
  163a0afe7fkb1ba2acd04c11ef0eefe8
  #    LogMeIn
  #    1024 bit - 128 Character URL
  72oxuj0fzefqo3fu04xjtvmd0adj2948rfh7g5by4forkwcy7t651z7hcb6kjjgqkxmvmfqpyrcfy15z1fto8ewcxstjc6avicag7d5qnoimsm19kb9kgi9i7v6z01d5
  </code></pre>
  
  <p>I'm leaning toward that 128 character, 1024 bit style, as it seems very secure. I guess I could make four MD5 hashes and merge them, but is that really effective?</p>
  
  <p>I have two specific intentions for a url such as this, but I'm sure there are others who may find this useful.</p>
  
  <p>1) Instant log in shortcut/icon for users</p>
  
  <p>2) Single-use url (Password recovery links)</p>