Paper 2018/005

Simple and Efficient Two-Server ORAM

S. Dov Gordon, Jonathan Katz, and 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.

Available format(s)
Cryptographic protocols
Publication info
Published elsewhere. Asiacrypt 2018
ORAMsingle-roundmulti-party computationRAM model
Contact author(s)
wangxiao @ cs umd edu
2018-09-05: last of 3 revisions
2018-01-02: received
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      author = {S.  Dov Gordon and Jonathan Katz and Xiao Wang},
      title = {Simple and Efficient Two-Server ORAM},
      howpublished = {Cryptology ePrint Archive, Paper 2018/005},
      year = {2018},
      note = {\url{}},
      url = {}
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