Efficient Private Information Retrieval Over Unsynchronized Databases

Fanti, Giulia; Ramchandran, Kannan

doi:10.1109/jstsp.2015.2432740

Cited by 37 publications

(38 citation statements)

References 25 publications

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“…Finally, we denote D as the expected number of downloaded bits with respect to different realization of the cached bit indices, i.e., D = E H [D H ]. A pair (D, L) is achievable if there exists a PIR scheme satisfying the reliability constraint (7) and the privacy constraint (8). The optimal normalized download cost D * is defined as…”

Section: Usermentioning

confidence: 99%

“…A simple but highly inefficient way is to download all the files from a particular database, which results in the normalized download cost of D L = K, where L is the file size and D is the total number of downloaded bits from the N databases. The PIR problem has originated in the computer science community [1][2][3][4][5] and has drawn attention in the information theory society with early examples [6][7][8][9][10][11]. Recently, Sun and Jafar [12] have characterized the optimal normalized download cost for the classical PIR problem to be D L = 1 + 1 N + · · · + 1 N K−1 .…”

Section: Introductionmentioning

confidence: 99%

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The Capacity of Private Information Retrieval from Decentralized Uncoded Caching Databases

et al. 2019

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We consider the private information retrieval (PIR) problem from decentralized uncoded caching databases. There are two phases in our problem setting, a caching phase, and a retrieval phase. In the caching phase, a data center containing all the K files, where each file is of size L bits, and several databases with storage size constraint µKL bits exist in the system. Each database independently chooses µKL bits out of the total KL bits from the data center to cache through the same probability distribution in a decentralized manner. In the retrieval phase, a user (retriever) accesses N databases in addition to the data center, and wishes to retrieve a desired file privately. We characterize the optimal normalized download cost to be D L = N +1 n=1 N n−1 µ n−1 (1 − µ) N +1−n 1 + 1 n + · · · + 1 n K−1 . We show that uniform and random caching scheme which is originally proposed for decentralized coded caching by Maddah-Ali and Niesen, along with Sun and Jafar retrieval scheme which is originally proposed for PIR from replicated databases surprisingly result in the lowest normalized download cost. This is the decentralized counterpart of the recent result of Attia, Kumar and Tandon for the centralized case. The converse proof contains several ingredients such as interference lower bound, induction lemma, replacing queries and answering string random variables with the content of distributed databases, the nature of decentralized uncoded caching databases, and bit marginalization of joint caching distributions.

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Section: Usermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Capacity of Private Information Retrieval from Decentralized Uncoded Caching Databases

et al. 2019

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“…To fully characterize the storage system in this case, we represent the storage system as R-regular graph 1 ; see Fig. 1 and Table 1 for a (6,3,2,9) example. We characterize the storage system by a (V, E) regular graph, where V = W = {W 1 , W 2 , · · · , W K } is the set of vertices, and E = D = {D 1 , D 2 , · · · , D N } is the set of edges, i.e., in this graph, the vertices are the messages and the edges are the databases.…”

Section: Problem Formulationmentioning

confidence: 99%

“…In the classical setting, a user is interested in retrieving a single message (file) out of K messages from N replicated and non-colluding databases, in such a way that no database can know the identity of the user's desired file. The PIR problem has become a vibrant research topic within information theory starting with trailblazing papers [2][3][4][5][6][7][8]. In [9], Sun and Jafar introduce the PIR capacity, which is the supremum of the ratio of the number of bits of desired information (L) that can be retrieved privately to the total downloaded information.…”

Section: Introductionmentioning

confidence: 99%

Private Information Retrieval from Non-Replicated Databases

Banawan

Ulukuş

2019

2019 IEEE International Symposium on Information Theory (ISIT)

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We consider the problem of private information retrieval (PIR) of a single message out of K messages from N non-colluding and non-replicated databases. Different from the majority of the existing literature, which considers the case of replicated databases where all databases store the same content in the form of all K messages, here, we consider the case of non-replicated databases under a special non-replication structure where each database stores M out of K messages and each message is stored across R different databases. This generates an R-regular graph structure for the storage system where the vertices of the graph are the messages and the edges are the databases. We derive a general upper bound for M = 2 that depends on the graph structure. We then specialize the problem to storage systems described by two special types of graph structures: cyclic graphs and fully-connected graphs. We prove that the PIR capacity for the case of cyclic graphs is 2 K+1 , and the PIR capacity for the case of fully-connected graphs is min{ 2 K , 1 2 }. To that end, we propose novel achievable schemes for both graph structures that are capacity-achieving. The central insight in both schemes is to introduce dependency in the queries submitted to databases that do not contain the desired message, such that the requests can be compressed. In both cases, the results show severe degradation in PIR capacity due to non-replication.

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“…The informationtheoretic formulation of the BPIR problem was proposed in [39], where a subset of databases with size B may introduce arbitrary errors to the answers of the user's query. This may be done unintentionally, for example, when some databases' contents are not up to date [40], or intentionally, when some databases introduce errors in their answers to prevent the user from correctly decoding the desired message. While the user knows the number B, it does not know which set of B databases are byzantine.…”

Section: Introductionmentioning

confidence: 99%

The Capacity of Multi-round Private Information Retrieval from Byzantine Databases

Yao

Liu

Kang

2019

2019 IEEE International Symposium on Information Theory (ISIT)

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In this work, we investigate the capacity of private information retrieval (PIR) from N replicated databases, where a subset of the databases are untrustworthy (byzantine) in their answers to the query of the user. We allow for multi-round queries and demonstrate that the identities of the byzantine databases can be determined with a small additional download cost. As a result, the capacity of the multi-round PIR with byzantine databases (BPIR) reaches that of the robust PIR problem when the number of byzantine databases is less than the number of trustworthy databases.

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Efficient Private Information Retrieval Over Unsynchronized Databases

Cited by 37 publications

References 25 publications

The Capacity of Private Information Retrieval from Decentralized Uncoded Caching Databases

The Capacity of Private Information Retrieval from Decentralized Uncoded Caching Databases

Private Information Retrieval from Non-Replicated Databases

The Capacity of Multi-round Private Information Retrieval from Byzantine Databases

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