[Resource Topic] 2018/005: Simple and Efficient Two-Server ORAM

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Simple and Efficient Two-Server ORAM

Authors: S. Dov Gordon, Jonathan Katz, Xiao Wang


We show a protocol for two-server oblivious RAM (ORAM) that is simpler and more efficient than the best prior work. Our construction combines any tree-based ORAM with an extension of a two-server private information retrieval scheme by Boyle et al., and is able to avoid recursion and thus use only one round of interaction. In addition, our scheme has a very cheap initialization phase, making it well suited for RAM-based secure computation. Although our scheme requires the servers to perform a linear scan over the entire data, the cryptographic computation involved consists only of block-cipher evaluations. A practical instantiation of our protocol has excellent concrete parameters: for storing an N-element array of arbitrary size data blocks with statistical security parameter \lambda, the servers each store 4N encrypted blocks, the client stores \lambda+2\log N blocks, and the total communication per logical access is roughly 10 \log N encrypted blocks.

ePrint: https://eprint.iacr.org/2018/005

Slides: https://asiacrypt.iacr.org/2018/files/SLIDES/WEDNESDAY/P514/1550-1640/gordon.pdf

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