Last Path Caching: A Simple Way to Remove Redundant Memory Accesses of Path ORAM

Oblivious RAM (ORAM) is a technique to hide the access pattern of data to untrusted memory along with their contents. Path ORAM is a recent lightweight ORAM protocol, whose derived access pattern involves some redundancy that can be removed without the loss of security. In this paper, we introduce last path caching, which removes the redundancy of Path ORAM with a simpler protocol than an existing scheme. By combining two caching strategies, our technique showed only 0.2% performance loss from the existing one, while keeping the determinacy of the derived access pattern.