Ghost routing to enable oblivious computation on memory-centric networks

Abstract

With offloading of data to the cloud, ensuring privacy and securing data has become more important. However, encrypting data alone is insufficient as the memory address itself can leak sensitive information. In this work, we exploit packetized memory interface to provide secure memory access and support oblivious computation in a system with multiple memory modules interconnected with a multi-hop, memory-centric network. While the memory address can be encrypted with a packetized memory interface, simply encrypting the address does not provide full oblivious computation since coarse-grain memory access patterns can be leaked. In this work, we first propose a scalable encryption microarchitecture with source-based routing where the packet is only encrypted once at source and latency overhead in intermediate routers is minimized. We then define secure routing in memory-centric networks to enable oblivious computation such that memory access patterns across the memory modules are completely obfuscated. We explore different naive secure routing algorithms to ensure oblivious computation but they come with high performance overhead. To minimize performance overhead, we propose ghost packets that replace dummy packets with existing network traffic. We also propose Ghost routing that batches multiple ghost packets together to minimize bandwidth loss from naive secure routing while exploiting random routing.