Paper 2019/531

How to Correct Errors in Multi-Server PIR

Kaoru Kurosawa


Suppose that there exist a user and $\ell$ servers $S_1, \ldots, S_{\ell}$. Each server $S_j$ holds a copy of a database $x=(x_1, \ldots, x_n) \in \{0,1\}^n$, and the user holds a secret index $i_0 \in \{1, \ldots, n\}$. A b error correcting $\ell$ server PIR (Private Information Retrieval) scheme allows a user to retrieve $x_{i_0}$ correctly even if and $b$ or less servers return false answers while each server learns no information on $i_0$ in the information theoretic sense. Although there exists such a scheme with the total communication cost $O(n^{1/(2k-1)} \times k\ell \log{\ell})$ where $k=\ell-2b$, the decoding algorithm is very inefficient. In this paper, we show an efficient decoding algorithm for this $b$ error correcting $\ell$ server PIR scheme. It runs in time $O(\ell^3)$.

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Publication info
A minor revision of an IACR publication in Asiacrypt 2019
Private Information Retrievalinformation theoreticerror correcting
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kaoru kurosawa kk @ vc ibaraki ac jp
2019-09-04: last of 2 revisions
2019-05-21: received
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      author = {Kaoru Kurosawa},
      title = {How to Correct Errors in Multi-Server PIR},
      howpublished = {Cryptology ePrint Archive, Paper 2019/531},
      year = {2019},
      note = {\url{}},
      url = {}
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