Boomerang: Metadata-Private Messaging under Hardware Trust


Peipei Jiang, Wuhan University and City University of Hong Kong; Qian Wang and Jianhao Cheng, Wuhan University; Cong Wang, City University of Hong Kong; Lei Xu, Nanjing University of Science and Technology; Xinyu Wang, Tencent Inc.; Yihao Wu and Xiaoyuan Li, Wuhan University; Kui Ren, Zhejiang University


In end-to-end encrypted (E2EE) messaging systems, protecting communication metadata, such as who is communicating with whom, at what time, etc., remains a challenging problem. Existing designs mostly fall into the balancing act among security, performance, and trust assumptions: 1) designs with cryptographic security often use hefty operations, incurring performance roadblocks and expensive operational costs for large-scale deployment; 2) more performant systems often follow a weaker security guarantee, like differential privacy, and generally demand more trust from the involved servers. So far, there has been no dominant solution. In this paper, we take a different technical route from prior art, and propose Boomerang, an alternative metadata-private messaging system leveraging the readily available trust assumption on secure enclaves (as those emerging in the cloud). Through a number of carefully tailored oblivious techniques on message shuffling, workload distribution, and proactive patching of the communication pattern, Boomerang brings together low latency, horizontal scalability, and cryptographic security, without prohibitive extra cost. With 32 machines, Boomerang achieves 99th percentile latency of 7.76 seconds for 220 clients. We hope Boomerang offers attractive alternative options to the current landscape of metadata-private messaging designs.

NSDI '23 Open Access Sponsored by
King Abdullah University of Science and Technology (KAUST)

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@inproceedings {286423,
author = {Peipei Jiang and Qian Wang and Jianhao Cheng and Cong Wang and Lei Xu and Xinyu Wang and Yihao Wu and Xiaoyuan Li and Kui Ren},
title = {Boomerang: {Metadata-Private} Messaging under Hardware Trust},
booktitle = {20th USENIX Symposium on Networked Systems Design and Implementation (NSDI 23)},
year = {2023},
isbn = {978-1-939133-33-5},
address = {Boston, MA},
pages = {877--899},
url = {},
publisher = {USENIX Association},
month = apr,

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