[Resource Topic] 2023/903: Near-Optimal Oblivious Key-Value Stores for Efficient PSI, PSU and Volume-Hiding Multi-Maps

Welcome to the resource topic for 2023/903

Title:
Near-Optimal Oblivious Key-Value Stores for Efficient PSI, PSU and Volume-Hiding Multi-Maps

Authors: Alexander Bienstock, Sarvar Patel, Joon Young Seo, Kevin Yeo

Abstract:

In this paper, we study oblivious key-value stores (OKVS) that enable encoding n key-value pairs into length m encodings while hiding the input keys. The goal is to obtain high rate, n/m, with efficient encoding and decoding algorithms. We present \mathsf{RB\text{-}OKVS} built on random band matrices that obtains near-optimal rates as high as 0.97 whereas prior works could only achieve rates up to 0.81 with similar encoding times.

Using \mathsf{RB\text{-}OKVS}, we obtain state-of-the-art protocols for private set intersection (PSI) and union (PSU). Our semi-honest PSI has up to 12% smaller communication and 13% reductions in monetary cost with slightly larger computation. We also obtain similar improvements for both malicious and circuit PSI. For PSU, our protocol obtains improvements of up to 22% in communication, 40% in computation and 21% in monetary cost. In general, we obtain the most communication- and cost-efficient protocols for all the above primitives.

Finally, we present the first connection between OKVS and volume-hiding encrypted multi-maps (VH-EMM) where the goal is to outsource storage of multi-maps while hiding the number of values associated with each key (i.e., volume). We present \mathsf{RB\text{-}MM} with 16% smaller storage, 5x faster queries and 8x faster setup than prior works.

ePrint: https://eprint.iacr.org/2023/903

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