Private Information Retrieval Research Papers (original) (raw)

We consider the problem of multi-message private information retrieval (MPIR) from N non-communicating replicated databases. In MPIR, the user is interested in retrieving P messages out of M stored messages without leaking the identity of... more

We consider the problem of multi-message private information retrieval (MPIR) from N non-communicating replicated databases. In MPIR, the user is interested in retrieving P messages out of M stored messages without leaking the identity of the retrieved messages. The information-theoretic sum capacity of MPIR C P s is the maximum number of desired message symbols that can be retrieved privately per down-loaded symbol. For the case P ≥ M 2 , we determine the exact sum capacity of MPIR as C P s = 1 1+ M −P P N. The achievable scheme in this case is based on downloading MDS-coded mixtures of all messages. For P ≤ M 2 , we develop lower and upper bounds for all M, P, N. These bounds match if the total number of messages M is an integer multiple of the number of desired messages P , i.e., M P ∈ N. In this case, C P s = 1− 1 N 1−(1 N) M/P. The achievable scheme in this case generalizes the single-message capacity achieving scheme to have unbalanced number of stages per round of download. For all the remaining cases, the difference between the lower and upper bound is at most 0.0082, which occurs for M = 5, P = 2, N = 2. Our results indicate that joint retrieval of desired messages is more efficient than successive use of single-message retrieval schemes.

—We consider the problem of private information retrieval (PIR) over a distributed storage system. The storage system consists of N non-colluding databases, each storing an MDS-coded version of M messages. In the PIR problem, the user... more

—We consider the problem of private information retrieval (PIR) over a distributed storage system. The storage system consists of N non-colluding databases, each storing an MDS-coded version of M messages. In the PIR problem, the user wishes to retrieve one of the available messages without revealing the message identity to any individual database. We derive the information-theoretic capacity of this problem, which is defined as the maximum number of bits of the desired message that can be privately retrieved per one bit of downloaded information. We show that the PIR capacity in this case is C = 1 + K N + K 2 N 2 + · · · + K M −1 N M −1 −1 = (1 + Rc + R 2 c + · · · + R M −1 c) −1 = 1−Rc 1−R M c , where Rc is the rate of the (N, K) code used. The capacity is a function of the code rate and the number of messages only regardless of the explicit structure of the storage code. The result implies a fundamental tradeoff between the optimal retrieval cost and the storage cost. The result generalizes the achievability and converse results for the classical PIR with replicating databases to the case of coded databases.

In today’s modern world, it is very easy for a person to know his/her location with the help of devices having GPS facility. When user’s location is provided to LBS, it is possible to user to know all location dependent information like... more

In today’s modern world, it is very easy for a person to know his/her location with the help of devices having GPS facility. When user’s location is provided to LBS, it is possible to user to know all location dependent information like location of friends or Nearest Restaurant, whether or traffic conditions. The massive use of mobile devices pave the way for the creation of wireless networks that can be used to exchange information based on locations. When the exchange of location information is done amongst entrusted parties, the privacy of the user could be in harmful. Existing protocol doesn’t work on many different mobile devices and another issue is that, Location Server (LS) should provide misleading data to user. So we are working on enhancement of this protocol.

Mobile devices with global positioning capabilities allow users to retrieve points of interest (POI) in their proximity. To protect user privacy, it is important not to disclose exact user coordinates to un-trusted entities that provide... more

Mobile devices with global positioning capabilities allow users to retrieve points of interest (POI) in their proximity. To protect user privacy, it is important not to disclose exact user coordinates to un-trusted entities that provide location-based services. Currently, there are two main approaches to protect the location privacy of users:(i) hiding locations inside cloaking regions (CRs) and (ii) encrypting location data using private information retrieval (PIR) protocols. Previous work focused on finding good trade-offs between privacy and ...

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... more

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 KKK files, where each file is of size LLL bits, and several databases with storage size constraint muKL\mu K LmuKL bits exist in the system. Each database independently chooses muKL\mu K LmuKL bits out of the total KLKLKL bits from the data center to cache through the same probability distribution in a decentralized manner. In the retrieval phase, a user (retriever) accesses NNN databases in addition to the data center, and wishes to retrieve a desired file privately. We characterize the optimal normalized download cost to be fracDL=sumn=1N+1binomNn−1mun−1(1−mu)N+1−nleft(1+frac1n+dots+frac1nK−1right)\frac{D}{L} = \sum_{n=1}^{N+1} \binom{N}{n-1} \mu^{n-1} (1-\mu)^{N+1-n} \left( 1+ \frac{1}{n} + \dots+ \frac{1}{n^{K-1}} \right)fracDL=sumn=1N+1binomNn−1mun−1(1−mu)N+1−nleft(1+frac1n+dots+frac1nK−1right). We show that uniform and random caching scheme which is originally proposed for decentralized coded c...

We consider the problem of single-round private information retrieval (PIR) from N replicated databases. We consider the case when B databases are outdated (unsyn-chronized), or even worse, adversarial (Byzantine), and therefore, can... more

We consider the problem of single-round private information retrieval (PIR) from N replicated databases. We consider the case when B databases are outdated (unsyn-chronized), or even worse, adversarial (Byzantine), and therefore, can return incorrect answers. In the PIR problem with Byzantine databases (BPIR), a user wishes to retrieve a specific message from a set of M messages with zero-error, irrespective of the actions performed by the Byzantine databases. We consider the T-privacy constraint in this paper, where any T databases can collude, and exchange the queries submitted by the user. We derive the information-theoretic capacity of this problem, which is the maximum number of correct symbols that can be retrieved privately (under the T-privacy constraint) for every symbol of the downloaded data. We determine the exact BPIR capacity to be C = N −2B N · 1− T N−2B 1−(T N−2B) M , if 2B + T < N. This capacity expression shows that the effect of Byzantine databases on the retrieval rate is equivalent to removing 2B databases from the system, with a penalty factor of N −2B N , which signifies that even though the number of databases needed for PIR is effectively N − 2B, the user still needs to access the entire N databases. The result shows that for the unsyn-chronized PIR problem, if the user does not have any knowledge about the fraction of the messages that are mis-synchronized, the single-round capacity is the same as the BPIR capacity. Our achievable scheme extends the optimal achievable scheme for the robust PIR (RPIR) problem to correct the errors introduced by the Byzantine databases as opposed to erasures in the RPIR problem. Our converse proof uses the idea of the cut-set bound in the network coding problem against adversarial nodes.

Privacy remains a major concern when using search engines to find for information on the web due to the fact that search engines own massive resources in preserving search logs of each user and organizations. However, many of the present... more

Privacy remains a major concern when using search engines to find for information on the web due to the fact that search engines own massive resources in preserving search logs of each user and organizations. However, many of the present query search privacy practices require the very same search engine and third party to collaborate, making privacy even more difficult. Therefore, as a contribution, we present a heuristic, permutation of web search query types, a non-cryptographic heuristic that works by formation of obfuscated search queries via permutation of query keyword categories. Preliminary results from this study show that web search query and specific user intent privacy might be achievable from the user side without involvement of the search engine or other third parties by the permutation of web search query types.

We propose a new keyword-based Private Information Retrieval (PIR) model that allows private modification of the database from which information is requested. In our model, the database is distributed over n servers, any one of which can... more

We propose a new keyword-based Private Information Retrieval (PIR) model that allows private modification of the database from which information is requested. In our model, the database is distributed over n servers, any one of which can act as a transparent interface for clients. We present protocols that support operations for accessing data, focusing on privately appending labelled records to the database (push) and privately retrieving the next unseen record appended under a given label (pull). The communication complexity between the client and servers is independent of the number of records in the database (or more generally, the number of previous push and pull operations) and of the number of servers. Our scheme also supports access control oblivious to the database servers by implicitly including a public key in each push, so that only the party holding the private key can retrieve the record via pull. To our knowledge, this is the first system that achieves the following properties: private database modification, private retrieval of multiple records with the same keyword, and oblivious access control. We also provide a number of extensions to our protocols and, as a demonstrative application, an unlinkable anonymous communication service using them.

With the advancement of the web it is very difficult to keep up with the amplifying requirements of learning on web, to satisfy user’s expectation. Users demand with the updated and accurate results. To solve the queries Search Engines... more

With the advancement of the web it is very difficult to keep up with the amplifying requirements of learning
on web, to satisfy user’s expectation. Users demand with the updated and accurate results. To solve the
queries Search Engines use different techniques. Google the most famous search engine uses Page Ranking
Algorithm. Ranking Algorithms arrange the results according to the user’s needs. This paper deals with
“Page Rank Algorithm”. Our proposed algorithm is an extension of page rank algorithm which refines the
results so that user gets what he/she expects. We have used a measure Average Precision to compare Page
Rank algorithm and the proposed algorithm, and proved that our algorithm provides better results.

One of the most important problems facing any distributed application over a heteroge-neous network is the protection of private sensitive information in local terminals. A subfield of cryptography called Secure Multiparty Computation... more

One of the most important problems facing any distributed application over a heteroge-neous network is the protection of private sensitive information in local terminals. A subfield of cryptography called Secure Multiparty Computation (SMC) is the study of such distributed computation protocols that allow distrusted parties to perform joint computation without dis-closing private data. SMC is increasingly used in diverse fields from data mining to computer vision. This paper provides a tutorial on SMC for non-experts in cryptography and surveys some of the latest advances in this exciting area including various schemes for reducing commu-nication and computation complexity of SMC protocols, doubly homomorphic encryption and private information retrieval. The proliferation of capturing and storage devices as well as the ubiquitous presence of com-puter networks make sharing of data easier than ever. Such pervasive exchange of data, however, has increasingly raised questions on how se...

While search engines have become vital tools for searching information on the Internet, privacy issues remain a growing concern due to the technological abilities of search engines to retain user search logs. Although such capabilities... more

While search engines have become vital tools for searching information on the Internet, privacy issues remain a growing concern due to the technological abilities of search engines to retain user search logs. Although such capabilities might provide enhanced personalized search results, the confidentiality of user intent remains uncertain. Even with web search query obfuscation techniques , another challenge remains, namely, reusing the same obfuscation methods is problematic, given that search engines have enormous computation and storage resources for query disambiguation. A number of web search query privacy procedures involve the cooperation of the search engine, a non-trusted entity in such cases, making query obfuscation even more challenging. In this study, we provide a review on how search engines work in regards to web search queries and user intent. Secondly, this study reviews material in a manner accessible to those outside computer science with the intent to introduce knowledge of web search engines to enable non-computer scientists to approach web search query privacy innovatively. As a contribution, we identify and highlight areas open for further investigative and innovative research in regards to end-user personalized web search privacy—that is methods that can be executed on the user side without third party involvement such as, search engines. The goal is to motivate future web search obfuscation heuristics that give users control over their personal search privacy.

Several compositional forms of simulation-based security have been proposed in the literature, including Universal Composability, Black-Box Simulatability, and variants thereof. These relations between a protocol and an ideal... more

Several compositional forms of simulation-based security have been proposed in the literature, including Universal Composability, Black-Box Simulatability, and variants thereof. These relations between a protocol and an ideal functionality are similar enough that they can be ordered from strongest to weakest according to the logical form of their definitions. However, determining whether two relations are in fact identical depends on some subtle features that have not been brought out in previous studies. We identify two main factors: the position of a “master process” in the distributed system and some limitations on transparent message forwarding within computational complexity bounds. Using a general computational framework, called Sequential Probabilistic Process Calculus (SPPC), we clarify the relationships between the simulation-based security conditions. Many of the proofs are carried out based on a small set of equivalence principles involving processes and distributed systems. These equivalences exhibit the essential properties needed to prove relationships between security notions and allow us to carry over our results to those computational models which satisfy these equivalences.