title: Encryption/Decryption on string
body: <p>I am very new to encryption and I would really appreciate your input on this puzzle as I am stuck.</p>
  
  <p>The puzzle:</p>
  
  <pre><code>&lt;?php&gt; blinker
  defined( '_JEXEC' ) or die( 'Restricted access' );
  </code></pre>
  
  <p>terminal:~ A fantastic internship opportunity...</p>
  
  <p>-bash: Solve this puzzle
  If you’re interested then <code>21613@23151811.co.za = fun@work.co.za</code>
  which will lead you to <code>171225.13916.co.za</code></p>
  
  <p>terminal:~ what is the answer$</p>
  
  <p>Please note I will not be entering with the answer I am just so interested as to how to solve this.</p>