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1. AB-ORAM: Constructing Adjustable Buckets for Space Reduction in Ring ORAM

   https://doi.org/10.1109/HPCA56546.2023.10071064  

   Raoufi, Mehrnoosh; Yang, Jun; Tang, Xulong; Zhang, Youtao (February 2023, IEEE International Symposium on High-Performance Computer Architecture)
2. H-ORAM: A Cacheable ORAM Interface for Efficient I/O Accesses

   https://doi.org/10.1145/3316781.3317841  

   Liu, Liang; Wang, Rujia; Zhang, Youtao; Yang, Jun (June 2020, Proceedings of the 56th Annual Design Automation Conference 2019)
3. ρ: Relaxed Hierarchical ORAM

   https://doi.org/10.1145/3297858.3304045  

   Nagarajan, Chandrasekhar; Shafiee, Ali; Balasubramonian, Rajeev; Tiwari, Mohit (January 2019, ASPLOS '19 Proceedings of the Twenty-Fourth International Conference on Architectural Support for Programming Languages and Operating Systems)

   Applications in the cloud are vulnerable to several attack scenarios. In one possibility, an untrusted cloud operator can examine addresses on the memory bus and use this information leak to violate privacy guarantees, even if data is encrypted. The Oblivious RAM (ORAM) construct was introduced to eliminate such information leak and these frameworks have seen many innovations in recent years. In spite of these innovations, the overhead associated with ORAM is very significant. This paper takes a step forward in reducing ORAM memory bandwidth overheads. We make the case that, similar to a cache hierarchy, a lightweight ORAM that fronts the full-fledged ORAM provides a boost in efficiency. The lightweight ORAM has a smaller capacity and smaller depth, and it can relax some of the many constraints imposed on the full-fledged ORAM. This yields a 2-level hierarchy with a relaxed ORAM and a full ORAM. The relaxed ORAM adopts design parameters that are optimized for efficiency and not capacity. We introduce a novel metadata management technique to further reduce the bandwidth for relaxed ORAM access. Relaxed ORAM accesses preserve the indistinguishability property and are equipped with an integrity verification system. Finally, to eliminate information leakage through LLC and relaxed ORAM hit rates, we introduce a deterministic memory scheduling policy. On a suite of memory-intensive applications, we show that the best Relaxed Hierarchical ORAM (ρ) model yields a performance improvement of 50%, relative to a Freecursive ORAM baseline. 

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4. D-ORAM: Path-ORAM Delegation for Low Execution Interference on Cloud Servers with Untrusted Memory

   https://doi.org/10.1109/HPCA.2018.00043  

   Wang, Rujia; Zhang, Youtao; Yang, Jun (February 2018, 2018 IEEE International Symposium on High Performance Computer Architecture (HPCA))
5. S ³ ORAM: A Computation-Efficient and Constant Client Bandwidth Blowup ORAM with Shamir Secret Sharing

   https://doi.org/10.1145/3133956.3134090  

   Hoang, Thang; Ozkaptan, Ceyhun D.; Yavuz, Attila A.; Guajardo, Jorge; Nguyen, Tam (November 2017, The ACM Conference on Computer and Communications Security (CCS))

   Oblivious Random Access Machine (ORAM) enables a client to access her data without leaking her access patterns. Existing client-efficient ORAMs either achieve O(log N) client-server communication blowup without heavy computation, or O(1) blowup but with expensive homomorphic encryptions. It has been shown that O(log N) bandwidth blowup might not be practical for certain applications, while schemes with O(1) communication blowup incur even more delay due to costly homomorphic operations. In this paper, we propose a new distributed ORAM scheme referred to as Shamir Secret Sharing ORAM (S3ORAM), which achieves O(1) client-server bandwidth blowup and O(1) blocks of client storage without relying on costly partial homomorphic encryptions. S3ORAM harnesses Shamir Secret Sharing, tree-based ORAM structure and a secure multi-party multiplication protocol to eliminate costly homomorphic operations and, therefore, achieves O(1) clientserver bandwidth blowup with a high computational efficiency. We conducted comprehensive experiments to assess the performance of S3ORAM and its counterparts on actual cloud environments, and showed that S3ORAM achieves three orders of magnitude lower end-to-end delay compared to alternatives with O(1) client communication blowup (Onion-ORAM), while it is one order of magnitude faster than Path-ORAM for a network with a moderate bandwidth quality. We have released the implementation of S3ORAM for further improvement and adaptation. 

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