Path Oblivious Heap: Optimal and Practical Oblivious Priority Queue

Abstract

We propose Path Oblivious Heap, an extremely simple, practical, and optimal oblivious priority queue. Our construction also implies a practical and optimal oblivious sorting algorithm which we call Path Oblivious Sort. Not only are our algorithms asymptotically optimal, we show that their practical performance is only a small constant factor worse than insecure baselines. More specificially, assuming roughly logarithmic client private storage, Path Oblivious Heap consumes 2× to 7× more bandwidth than the ordinary insecure binary heap; and Path Oblivious Sort consumes 4.5× to 6× more bandwidth than the insecure Merge Sort. We show that these performance results improve existing works by 1-2 orders of magnitude. Finally, we evaluate our algorithm for a multi-party computation scenario and show 7x to 8x reduction in the number of symmetric encryptions relative to the state of the art1.