An Analysis on Randomness of Path ORAM for Light-weight Implementation

Oblivious RAM (ORAM) is a technique to prevent not only the data but also their access pattern from being observed. Path ORAM is a recently proposed ORAM protocol, whose safety relies on the derived access pattern being observed as a sequence of accesses to random paths. In this paper, we analyze the effect of pseudorandom number generators (PRNGs) on the randomness of the derived path sequence. Our evaluation showed that, even with weak PRNGs that fail some of the diehard tests, the derived path sequences passed more tests. These results may open a new way to a light-weight implementation of Path ORAM.