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Mercier, Hugues
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Mercier, Hugues
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hugues.mercier@unine.ch
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Voici les éléments 1 - 10 sur 15
- PublicationMétadonnées seulementConfidentiality-Preserving Publish/Subscribe: A Survey(2016-6-30)
; ; ; Publish/subscribe (pub/sub) is an attractive communication paradigm for large-scale distributed applications running across multiple administrative domains. Pub/sub allows event-based information dissemination based on constraints on the nature of the data rather than on pre-established communication channels. It is a natural fit for deployment in untrusted environments such as public clouds linking applications across multiple sites. However, pub/sub in untrusted environments leads to major confidentiality concerns stemming from the content-centric nature of the communications. This survey classifies and analyzes different approaches to confidentiality preservation for pub/sub, from applications of trust and access control models to novel encryption techniques. It provides an overview of the current challenges posed by confidentiality concerns and points to future research directions in this promising field. - PublicationMétadonnées seulementPerformance/Security Tradeoffs for Content-Based Routing Supported by Bloom FiltersContent-based routing is widely used in large-scale distribu-ted systems as it provides a loosely-coupled yet expressive form of communication: consumers of information register their interests by the means of subscriptions, which are subsequently used to determine the set of recipients of every message published in the system. A major challenge of content-based routing is security. Although some techniques have been proposed to perform matching of encrypted subscriptions against encrypted messages, their computational cost is very high. To speed up that process, it was recently proposed to embed Bloom filters in both subscriptions and messages to reduce the space of subscriptions that need to be tested. In this article, we provide a comprehensive analysis of the information leaked by Bloom filters when implementing such a “prefiltering” strategy. The main result is that although there is a fundamental trade-off between prefiltering efficiency and information leakage, it is practically possible to obtain good prefiltering while securing the scheme against leakages with some simple randomization techniques.
- PublicationMétadonnées seulementInfrastructure Provisioning for Scalable Content-based Routing: Framework and Analysis(2012-1-13)
; ; ; ; ; Content-based publish/subscribe is an attractive paradigm for designing large-scale systems, as it decouples producers of information from consumers. This provides extensive flexibility for applications, which can use a modular architecture. Using this architecture, each participant expresses its interest in events by means of filters on the content of those events instead of using pre-established communication channels. However, matching events against filters has a non-negligible processing cost. Scaling the infrastructure with the number of users or events requires appropriate provisioning of resources for each of the operations involved: routing and filtering. In this paper, we propose and describe a generic, modular, and scalable infrastructure for supporting high-performance content-based publish/subscribe. We analyze its properties and show how it dynamically scales in a realistic setting. Our results provide valuable insights into the design and deployment of scalable content-based routing infrastructures. - PublicationAccès libreWorst-case, information and all-blocks locality in distributed storage systems: An explicit comparisonDistributed storage systems often use erasure coding techniques to provide reliability while decreasing the storage overhead required by replication. Due to the drawbacks of standard MDS erasure-correcting codes, numerous coding schemes recently proposed for distributed storage systems target other metrics such as repair locality and repair bandwidth. Unfortunately, these schemes are not always practical, and for most of them locality covers information data only. In this article, we compare three explicit linear codes for three types of locality: a Reed-Solomon code for worst-case locality, a recently proposed pyramid code for information locality and the Hamming code HAM, an optimal locally repairable code directly built from its generator matrix for all-blocks locality. We also provide an efficient way for repairing HAM and show that for the same level of storage overhead HAM provides faster encoding, faster repair and lower repair bandwidth than the other two solutions while requiring less than fifty lines of code.
- PublicationMétadonnées seulementEfficient Key Updates through Subscription Re-encryption for Privacy-Preserving Publish/SubscribeContent-based publish/subscribe (pub/sub) is an appealing information dissemination paradigm for distributed systems. Consumers of data subscribe to a pub/sub service, typically offered through a distributed broker overlay, and indicate their interests as constraints over the information content. Publishers generate the information flow, which the brokers filter and route to the interested subscribers. Protecting the information confidentiality, and in particular the interests of subscribers, is an important concern when brokers are located in untrusted domains such as public clouds. Encrypted matching techniques allow untrusted brokers to store encrypted subscriptions and match them against encrypted publications. Updates of encryption keys regularly happen in such contexts due to changes in trust relations. These key updates cause the invalidation of stored encrypted subscriptions and force subscribers to re-encrypt and re-submit them. This long and costly operation impacts the pub/sub service continuity and performance. In this paper, we propose a novel technique that allows updating encrypted subscriptions directly at the brokers while maintaining privacy guarantees. We present an implementation of the technique for the ASPE encrypted matching scheme and prove the security of our extension. We evaluate its practical effectiveness through a prototype implementation including a dependable key dis- tribution protocol. Our experiments show the ability to handle key updates while preserving service continuity and performance.
- PublicationAccès libreOn the Cost of Safe Storage for Public Clouds: an Experimental Evaluation(: IEEE, 2016-9-26)
; ; ; - PublicationMétadonnées seulementEfficient and Confidentiality-Preserving Content-Based Publish/Subscribe with Prefiltering(2015-6-25)
; ; ; ; Content-based publish/subscribe provides a loosely-coupled and expressive form of communication for large-scale distributed systems. Confidentiality is a major challenge for publish/subscribe middleware deployed over multiple administrative domains. Encrypted matching allows confidentiality-preserving content-based filtering but has high performance overheads. It may also prevent the use of classical optimizations based on subscriptions containment. We propose a support mechanism that reduces the cost of encrypted matching, in the form of a prefiltering operator using Bloom filters and simple randomization techniques. This operator greatly reduces the amount of encrypted subscriptions that must be matched against incoming encrypted publications. It leverages subscription containment information when available, but also ensures that containment confidentiality is preserved otherwise. We propose containment obfuscation techniques and provide a rigorous security analysis of the information leaked by Bloom filters in this case. We conduct a thorough experimental evaluation of prefiltering under a large variety of workloads. Our results indicate that prefiltering is successful at reducing the space of subscriptions to be tested in all cases. We show that while there is a tradeoff between prefiltering efficiency and information leakage when using containment obfuscation, it is practically possible to obtain good prefiltering performance while securing the technique against potential leakages. - PublicationAccès libreBlockchain-Based Metadata Protection for Archival Systems(: IEEE, 2019-10-1)
; ; ; - PublicationAccès libreHave a Seat on the ErasureBench: Easy Evaluation of Erasure Coding Libraries for Distributed Storage SystemsWe present ErasureBench, an open-source framework to test and benchmark erasure coding implementations for distributed storage systems under realistic conditions. ErasureBench automatically instantiates and scales a cluster of storage nodes, and can seamlessly leverage existing failure traces. As a first example, we use ErasureBench to compare three coding implementations: a (10,4) Reed-Solomon (RS) code, a (10,6,5) locally repairable code (LRC), and a partition of the data source in ten pieces without error-correction. Our experiments show that LRC and RS codes require the same repair throughput when used with small storage nodes, since cluster and network management traffic dominate at this regime. With large storage nodes, read and write traffic increases and our experiments confirm the theoretical and practical tradeoffs between the storage overhead and repair bandwidth of RS and LRC codes.
- PublicationMétadonnées seulementA Performance Evaluation of Erasure Coding Libraries for Cloud-Based Data StoresErasure codes have been widely used over the last decade to implement reliable data stores. They offer interesting trade-offs between efficiency, reliability, and storage overhead. Indeed, a distributed data store holding encoded data blocks can tolerate the failure of multiple nodes while requiring only a fraction of the space necessary for plain replication, albeit at an increased encoding and decoding cost. There exists nowadays a number of libraries implementing several variations of erasure codes, which notably differ in terms of complexity and implementation-specific optimizations. Seven years ago, Plank et al. [14] have conducted a comprehensive performance evaluation of open-source erasure coding libraries available at the time to compare their raw performance and measure the impact of different parameter configurations. In the present experimental study, we take a fresh perspective at the state of the art of erasure coding libraries. Not only do we cover a wider set of libraries running on modern hardware, but we also consider their efficiency when used in realistic settings for cloud-based storage, namely when deployed across several nodes in a data centre. Our measurements therefore account for the end-to-end costs of data accesses over several distributed nodes, including the encoding and decoding costs, and shed light on the performance one can expect from the various libraries when deployed in a real system. Our results reveal important differences in the efficiency of the different libraries, notably due to the type of coding algorithm and the use of hardware-specific optimizations.