Skiplist Timing Attack Vulnerability

Abstract

In this paper we address the structure and behavior of the probabilistic Skiplist data structure and present an exploit in the form of a timing attack on the structure. In this exploit, we show how to map the presumably hidden structure of a Skiplist by timing the return time of search queries. This data can then be used to perform operations on the Skiplist which will cause a degradation in its subsequent performance. In addition, we describe another exploitation of this data to use the Skiplist as a means of creating a hidden channel between two attackers. Finally, we propose a new variant of Skiplist we call a Splay Skiplist, which retains the $O(\log n)$ performance of Skiplist while defending against the stated exploit.