title: hash salt complexity
body: <p>Is there any benefit to using:</p>
  
  <pre><code>sha1($long_unpredictable_randomly_generated_salt.$password.$global_salt)
  </code></pre>
  
  <p>over </p>
  
  <pre><code>sha1(sha1($username).$password.$global_salt)
  </code></pre>
  
  <p>The unique salt is obviously stored in the database, while the global salt is in a configuration file on the server.</p>
  
  <p>I know the purpsoe of a salt is just to be unique, and prevent pre-calculated hash tables.. so I see no reason the long hash generated by <code>sha1($username)</code> is not good enough.. but as security is very important, I thought i'd ask for informative advice here from somebody who may know better :-)</p>