title: MD5 collision for known input
body: <p>Is it possible to create a MD5 collision based on a known input value?</p>
  
  <p>So for example I have input string <code>abc</code> with MD5 <code>900150983cd24fb0d6963f7d28e17f72</code>.
  Now I want to add bytes to string <code>def</code> to get the same MD5 <code>900150983cd24fb0d6963f7d28e17f72</code>.</p>
  
  <p>(I know this is possible by bruteforcing and waiting a long time; I want to know if there is a more efficient way in doing this)</p>