Paper 2022/1082 Original: eprint.iacr.org/2022/1082 ↗

Assisted Private Information Retrieval

Abstract

Private Information Retrieval (PIR) addresses the cryptographic problem of hiding sensitive database queries from database operators. In practice, PIR schemes face the challenges of either high computational costs or restrictive security assumptions, resulting in a barrier to deployment. In this work, we introduce Assisted Private Information Retrieval (APIR), a new PIR framework for keyword-value databases generalizing multi-server PIR and relaxing its database consistency assumption. We propose the construction of Synchronized APIR, an efficient hybrid APIR scheme combining black-box single-server PIR and non-black-box multi-server PIR. To evaluate the scheme, we apply it to a proof-of-concept privacy-preserving DNS application. The experiment results demonstrate that Synchronized APIR outperforms the baseline single-server PIR protocol in communication and computational cost after the initial one-time cost.