title: HashDoS: how can worst case complexity of Hashtable be O(n^2)?
body: <p>By now many of you must have heard about <a href="http://cryptanalysis.eu/blog/2011/12/28/effective-dos-attacks-against-web-application-plattforms-hashdos/" rel="nofollow">HashDoS</a>. The researchers who found this, claim in <a href="http://www.youtube.com/watch?v=R2Cq3CLI6H8&amp;feature=youtu.be" rel="nofollow">their video</a> that the worst case complexity of Hastable is <code>O(n^2)</code>. How can this be?</p>