Private information retrieval (PIR) allows a client to retrieve any block xifrom a database x = x1xnsuch that i remains hidden from the database servers. PIR •protocols with unconditional privacy and sublinear (in n) communication complexity can be constructed assuming multiple honest-but-curious servers. This assumption however cannot be guaranteed in many real life scenarios such as using cloud servers as database servers. In this paper, we consider an information-theoretic PIR with result verification (PIR-RV) model where the servers may be dishonest (i.e., cheating) and provide incorrect answers but the client can detect the existence of cheating servers. We construct a 2-server PIR-RV protocol with communication complexity ${\mathcal{O}}({n^{1/2}}{\text{log }}p)$ where p is a parameter and controls the probability that the client fails to detect. Our idea may be extended to construct k-server PIR-RV protocols for k ≥ 3.
Private information retrieval (PIR) allows a client to retrieve any block xifrom a database x = x1xnsuch that i remains hidden from the database servers. PIR •protocols with unconditional privacy and sublinear (in n) communication complexity can be constructed assuming multiple honest-but-curious servers. This assumption however cannot be guaranteed in many real life scenarios such as using cloud servers as database servers. In this paper, we consider an information-theoretic PIR with result verification (PIR-RV) model where the servers may be dishonest (i.e., cheating) and provide incorrect answers but the client can detect the existence of cheating servers. We construct a 2-server PIR-RV protocol with communication complexity O(n1/2log p) where p is a parameter and controls the probability that the client fails to detect. Our idea may be extended to construct k-server PIR-RV protocols for k ≥ 3.
Private Information Retrieval (PIR) protocols allow a client to retrieve any file of interest while keeping the files identity hidden from the database servers. While many existing PIR protocols assume servers to be honest but curious, we investigate the scenario of dishonest servers that provide incorrect answers to mislead clients into obtaining wrong results. We propose a unified framework for polynomial PIR protocols encompassing various existing protocols that optimize the download rate or total communication cost. We introduce a way to transform a polynomial PIR to a verifiable one without increasing the number of involved servers by doubling the queries. The security guarantees can be information-theoretic or computational, and the verification keys can be public or private. Moreover, in one of our protocols, the ratio between the additional download overhead associated with verification and the normal download cost approaches zero as the file size goes to infinity.
Private Information Retrieval (PIR) allows clients to retrieve database entries without leaking retrieval indices, yet malicious servers seriously compromise retrieval correctness. Existing Authenticated PIR (APIR) schemes resist selective-failure attacks but rely on computational hardness assumptions. In contrast, information-theoretic PIR with Result Verification (itPIR-RV) achieves integrity without computational assumptions, yet only provides relaxed query privacy with no defense against selective-failure attacks. This paper focuses on unconditionally secure information-theoretic APIR (itAPIR) constructions. We propose the rigorous information-theoretic security definition for itAPIR with statistical privacy against selective-failure attacks and integrity as core properties, formalize the hierarchical relation between itAPIR and itPIR-RV as a relaxed variant with identical integrity but basic query privacy, and prove a conversion theorem that valid itPIR-RV schemes can be directly upgraded to secure itAPIR with no extra overhead. Our work bridges the theoretical gap, simplifies itAPIR design, and enables quantum-resistant PIR in malicious server environments.
A Private Information Retrieval (PIR) protocol allows a client to learn the ith row of a database held by one or more servers, without revealing i to the servers. A Random-Index PIR (RPIR) protocol, introduced by Gentry et al. (TCC 2021), is a PIR protocol where, instead of being chosen by the client, i is random. This has applications in e.g. anonymous committee selection. Both PIR and RPIR protocols are interesting only if the communication complexity is smaller than the database size; otherwise, the trivial solution where the servers send the entire database suffices. Unlike PIR, where the client must send at least one message (to encode information about i), RPIR can be executed in a single round of server-to-client communication. In this paper, we study such one-round, information-theoretic RPIR protocols. The only known construction in this setting is SimpleMSRPIR (Gentry et al.), which requires the servers to communicate approximately N/2 bits, N being the database size. We show an Ω(√N) lower bound on communication complexity for one-round two-server information-theoretic RPIR, and a sublinear upper bound. Finally, we show how to use a sublinear amount of database-independent correlated randomness among multiple servers to get near-optimal online communication complexity (the size of one row plus the size of one index description per server).
A Private Information Retrieval (PIR) protocol allows a client to learn the ith row of a database held by one or more servers, without revealing i to the servers. A Random-Index PIR (RPIR) protocol, introduced by Gentry et al. (TCC 2021), is a PIR protocol where, instead of being chosen by the client, i is random. This has applications in e.g. anonymous committee selection. Both PIR and RPIR protocols are interesting only if the communication complexity is smaller than the database size; otherwise, the trivial solution where the servers send the entire database suffices. Unlike PIR, where the client must send at least one message (to encode information about i), RPIR can be executed in a single round of server-to-client communication. In this paper, we study such one-round, information-theoretic RPIR protocols. The only known construction in this setting is SimpleMSRPIR (Gentry et al.), which requires the servers to communicate approximately N/2 bits, N being the database size. We show an Ω(√N) lower bound on communication complexity for one-round two-server information-theoretic RPIR, and a sublinear upper bound. Finally, we show how to use a sublinear amount of database-independent correlated randomness among multiple servers to get near-optimal online communication complexity (the size of one row plus the size of one index description per server).
Private Information Retrieval (PIR) protocols allow a user to read information from a database without revealing to the server storing the database which information he has read.Kushilevitz and Ostrovsky [23] construct, based on the quadratic residuosity assumption, a single-server PIR protc-co1 with small communication complexity.Cachin, Micali, and Stadler [6] present a single-server PIR protocol with a smaller communication complexity, based an the (new) *hiding assumption.A major question, addressed in the present work, is what assumption is the minimal assumption necessary for the construction of single-server private information retrieval protocols with small communication complexity.We prove that if there is a (O-error) PIR protocol in which the server sends less than n bits then one-way functions exist (where n is the number of bits in the database).That is, even saving one bit compared to the naive protocol, in which the entire database is sent, already requires one-way functions.The same result holds (but requires more work) even if we allow the retrieval to fail with probability of at most 1/(8n).Moreover, similar tcomputer science
In this paper, we investigate query processes and reconstruction functions for unconditionally secure 2-server 1-round binary private information retrieval (PIR) schemes. We begin by formulating a simplified model for PIR schemes which is equivalent to the usual model. We show that a query is equivalent to a boolean function of two variables, and we give a precise characterization of the boolean functions that can be used as "query pairs" to the two servers. We also consider several notions of "privacy" and we make a few remarks about the communication complexity of PIR schemes.