Explicit construction of exponential sized families of K-independent sets
Discrete Mathematics
New bounds for perfect hashing via information theory
European Journal of Combinatorics
CRYPTO '93 Proceedings of the 13th annual international cryptology conference on Advances in cryptology
Randomized algorithms
Lower Bounds on Formula Size of Boolean Functions Using Hypergraph Entropy
SIAM Journal on Discrete Mathematics
Theoretical Computer Science
Journal of the ACM (JACM)
Optimal linear perfect hash families
Journal of Combinatorial Theory Series A
Improved upper bounds on information-theoretic private information retrieval (extended abstract)
STOC '99 Proceedings of the thirty-first annual ACM symposium on Theory of computing
Communications of the ACM
Perfect hash families: probabilistic methods and explicit constructions
Journal of Combinatorial Theory Series A
Breaking the O(n1/(2k-1)) Barrier for Information-Theoretic Private Information Retrieval
FOCS '02 Proceedings of the 43rd Symposium on Foundations of Computer Science
Upper Bound on Communication Complexity of Private Information Retrieval
ICALP '97 Proceedings of the 24th International Colloquium on Automata, Languages and Programming
Hiding Instances in Multioracle Queries
STACS '90 Proceedings of the 7th Annual Symposium on Theoretical Aspects of Computer Science
STOC '84 Proceedings of the sixteenth annual ACM symposium on Theory of computing
Efficient multiplicative sharing schemes
EUROCRYPT'96 Proceedings of the 15th annual international conference on Theory and application of cryptographic techniques
Generalised Cumulative Arrays in Secret Sharing
Designs, Codes and Cryptography
Optimally robust private information retrieval
Security'12 Proceedings of the 21st USENIX conference on Security symposium
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A Private Information Retrieval (PIR) protocol allows a user to retrieve a data item of its choice from a database, such that the servers storing the database do not gain information on the identity of the item being retrieved. PIR protocols were studied in depth since the subject was introduced in Chor, Goldreich, Kushilevitz, and Sudan 1995. The standard definition of PIR protocols raises a simple question - what happens if some of the servers crash during the operation? How can we devise a protocol which still works in the presence of crashing servers? Current systems do not guarantee availability of servers at all times for many reasons, e.g., crash of server or communication problems. Our purpose is to design robust PIR protocols, i.e., protocols which still work correctly even if only k out of l servers are available during the protocols' operation (the user does not know in advance which servers are available). We present various robust PIR protocols giving different tradeoffs between the different parameters. These protocols are incomparable, i.e., for different values of n and k we will get better results using different protocols. We first present a generic transformation from regular PIR protocols to robust PIR protocols, this transformation is important since any improvement in the communication complexity of regular PIR protocol will immediately implicate improvement in the robust PIR protocol communication. We also present two specific robust PIR protocols. Finally, we present robust PIR protocols which can tolerate Byzantine servers, i.e., robust PIR protocols which still work in the presence of malicious servers or servers with corrupted or obsolete databases.