Helger Lipmaa's publications |

Helger Lipmaa and Kateryna Pavlyk. A Simpler Rate-Optimal CPIR Protocol. In Aggelos Kiayias, editor, *FC 2017*, volume ? of *Lecture Notes in Computer Science*, pages ?--?, Malta, April 3--7, 2017. Springer, Heidelberg. Accepted.

**File:**
[.pdf (387 KB)] __pdf recommended__.

**Abstract**:

In PETS 2015, Kiayias, Leonardos, Lipmaa, Pavlyk, and Tang proposed the first $(n, 1)$-CPIR protocol with rate $1 - o (1)$. They use advanced techniques from multivariable calculus (like the Newton-Puiseux algorithm) to establish optimal rate among a large family of different CPIR protocols. It is only natural to ask whether one can achieve similar rate but with a much simpler analysis. We propose parameters to the earlier $(n, 1)$-CPIR protocol of Lipmaa (ISC 2005), obtaining a CPIR protocol that is asymptotically almost as communication-efficient as the protocol of Kiayiaset al. However, for many relevant parameter choices, it is slightly more communication-efficient, due to the cumulative rounding errors present in the protocol of Kiayiaset al. Moreover, the new CPIR protocol is simpler to understand, implement, and analyze. The new CPIR protocol can be used to implement (computationally inefficient) FHE with rate $1 - o (1)$.

**Keywords:** Communication complexity, computationally-private information retrieval, cryptographic protocols, optimal rate.

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