Committed Private Information Retrieval


Chen Feng, Hong Yen Tran, Son Hoang Dau, Xun Yi, Emanuele Viterbo, Yu-Chih Huang, Jingge Zhu, Stanislav Kruglik, Han Mao Kiah, Quang Cao

Date of Publication


A private information retrieval (PIR) scheme allows a client to retrieve a data item xi among n items x1,x2,…,xn from k servers, without revealing what i is even when t<k servers collude and try to learn i. Such a PIR scheme is said to be t-private. A PIR scheme is v-verifiable if the client can verify the correctness of the retrieved xi even when v≤k servers collude and try to fool the client by sending manipulated data. Most of the previous works in the literature on PIR assumed that v<k, leaving the case of all-colluding servers open. We propose a generic construction that combines a linear map commitment (LMC) and an arbitrary linear PIR scheme to produce a k-verifiable PIR scheme, termed a committed PIR scheme. Such a scheme guarantees that even in the worst scenario, when all servers are under the control of an attacker, although the privacy is unavoidably lost, the client won't be fooled into accepting an incorrect xi. We demonstrate the practicality of our proposal by implementing the committed PIR schemes based on the Lai-Malavolta LMC and three well-known PIR schemes using the GMP library and blst, the current fastest C library for elliptic curve pairings.

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First Nations land acknowledegement

We acknowledge that the UBC Point Grey campus is situated on the traditional, ancestral, and unceded territory of the xʷməθkʷəy̓əm.

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