### Browsing by Author "Tajeddine, Razane"

Now showing 1 - 5 of 5

###### Results Per Page

###### Sort Options

Item Private Information Retrieval from Coded Storage(Aalto University, 2019) Tajeddine, Razane; Hollanti, Camilla, Prof., Aalto University, Department of Mathematics and Systems Analysis, Finland; El Rouayheb, Salim, Prof., Rutgers University, USA; Gnilke, Oliver, Dr., Aalto University, Department of Mathematics and Systems Analysis, Finland; Matematiikan ja systeemianalyysin laitos; Department of Mathematics and Systems Analysis; Perustieteiden korkeakoulu; School of Science; Hollanti, Camilla, Prof., Aalto University, Department of Mathematics and Systems Analysis, FinlandAlong with the technological advancements and the remarkable growth of digital data storage, new challenges arise regarding the reliabilty of the digital data storage and the privacy of the users. A distributed storage system (DSS) can store big amounts of data for a long time over possibly unreliable servers. As for the privacy concern of the users, much effort has been spent in trying to find systems and schemes that allow users to communicate, search, upload and download files while maintaining their privacy. One of those schemes is private information retrieval (PIR). PIR allows the users to hide the identity of files they request from a DSS. In other words, a PIR scheme allows the user to retrieve any file from a DSS without revealing the file identity to any of the servers. It goes without saying that, to achieve privacy, the user should download a bigger amount of data than the size of the desired file. The extra amount of data downloaded is quantified by the communication complexity of a PIR scheme. Naturally, downloading all the data from the DSS hides the identity of the desired file, but has a very high communication complexity, especially as the number of files in a DSS is typically very large. Moreover, this also raises the question of the server privacy, meaning that the user should not be able to retrieve any extra information about the undesired files while retrieving a certain file. Schemes taking into account the server privacy are called symmetric PIR (SPIR) schemes. This thesis focuses on constructing PIR schemes for different DSSs with low communication cost. We study different DSSs which reduce the storage cost of the system while providing reliability. We construct PIR schemes on such systems, where we consider both cases, the case where the servers in the DSS do not communicate, and the case where some subsets of the servers communicate in an effort to figure out the desired file identity. Moreover, we consider the SPIR problem, and consider the case where some servers may be unresponsive, such that they do not respond to the sent query, and the case where the servers may be malicious or unsynchronized and thus give false information to the user. Last but not least, this thesis also considers schemes providing privacy for users requesting data from a DSS over a random linear network.Item Private Information Retrieval from Coded Storage Systems with Colluding, Byzantine, and Unresponsive Servers(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019-06-01) Tajeddine, Razane; Gnilke, Oliver; Karpuk, David; Freij-Hollanti, Ragnar; Hollanti, Camilla; Department of Mathematics and Systems Analysis; Algebra and Discrete MathematicsThe problem of private information retrieval (PIR) from coded storage systems with colluding, Byzantine, and unresponsive servers is considered. An explicit scheme using an [n,k] Reed-Solomon storage code is designed, protecting against t-collusion, and handling up to b Byzantine and r unresponsive servers, when n>k+t+2b+r-1. This scheme achieves a PIR rate of ((n-r-(k+2b+t-1))/n-r). In the case where the capacity is known, namely, when k=1, it is asymptotically capacity achieving as the number of files grows. Finally, the scheme is adapted to symmetric PIR.Item Private Information Retrieval from MDS Coded Data in Distributed Storage Systems(2018-03-13) Tajeddine, Razane; Gnilke, Oliver W.; El Rouayheb, Salim; Department of Mathematics and Systems AnalysisThe problem of providing privacy, in the private information retrieval (PIR) sense, to users requesting data from a distributed storage system (DSS), is considered. The DSS is coded by an (n, k, d) Maximum Distance Separable (MDS) code to store the data reliably on unreliable storage nodes. Some of these nodes can be spies which report to a third party, such as an oppressive regime, which data is being requested by the user. An information theoretic PIR scheme ensures that a user can satisfy its request while revealing no information on which data is being requested to the nodes. A user can trivially achieve PIR by downloading all the data in the DSS. However, this is not a feasible solution due to its high communication cost. We construct PIR schemes with low download communication cost. When there is b = 1 spy node in the DSS, in other words, no collusion between the nodes, we construct PIR schemes with download cost 1/1–R per unit of requested data (R = k/n is the code rate), achieving the information theoretic limit for linear schemes. The proposed schemes are universal since they depend on the code rate, but not on the generator matrix of the code. Also, if b ≤ n — δk nodes collude, with δ = b ⌊ n—b/k ⌋, we construct linear PIR schemes with download cost b+δk/δ .Item Private Information Retrieval over Random Linear Networks(Institute of Electrical and Electronics Engineers, 2019-07-15) Tajeddine, Razane; Wachter-Zeh, Antonia; Hollanti, Camilla; Department of Mathematics and Systems Analysis; Algebra and Discrete Mathematics; Technische Universität MünchenIn this paper, the problem of providing privacy to users requesting data over a network from a distributed storage system (DSS) is considered. The DSS, which is considered as the multi-terminal destination of the network from the user’s perspective, is encoded by a maximum rank distance (MRD) code to store the data on these multiple servers. A private information retrieval (PIR) scheme ensures that a user can request a file without revealing any information on which file is being requested to any of the servers. In this paper, a novel PIR scheme is proposed, allowing the user to recover a file from a storage system with low communication cost, while allowing some servers in the system to collude in the quest of revealing the identity of the requested file. The network is modeled as a random linear network, i.e., all nodes of the network forward random (unknown) linear combinations of incoming packets. Both error-free and erroneous random linear networks are considered.Item Robust Private Information Retrieval from Coded Systems with Byzantine and Colluding Servers(2018-08-15) Tajeddine, Razane; Gnilke, Oliver W.; Karpuk, David; Freij-Hollanti, Ragnar; Hollanti, Camilla; Department of Mathematics and Systems Analysis; Universidad de los Andes Colombia; Technical University of MunichA private information retrieval (PIR) scheme on coded storage systems with colluding, byzantine, and non-responsive servers is presented. Furthermore, the scheme can also be used for symmetric PIR in the same setting. An explicit scheme using an [n, k] generalized Reed-Solomon storage code is designed, protecting against t-collusion and handling up to b byzantine and r non-responsive servers, when n\geq n^{\prime}=(\nu+1)k+t+2b+r-1, for some integer \nu\geq 1. This scheme achieves a PIR rate of 1-\frac{k+2b+t+r-1}{n^{\prime}-r}. In the case where the capacity is known, namely when k=1, it is asymptotically capacity achieving as the number of files grows.