Proofs of Retrievability are protocols which allow a Client to store data remotely and to efficiently ensure, via audits, that the entirety of that data is still intact. Dynamic Proofs of Retrievability (DPoR) also support efficient retrieval and update of any small portion of the data. We propose a novel protocol for arbitrary outsourced data storage that achieves both low remote storage size and audit complexity. A key ingredient, that can be also of intrinsic interest, reduces to efficiently evaluating a secret polynomial at given public points, when the (encrypted) polynomial is stored on an untrusted Server. The Server performs the evaluations and also returns associated certificates. A Client can check that the evaluations are correct using the certificates and some pre-computed keys, more efficiently than re-evaluating the polynomial. Our protocols support two important features: the polynomial itself can be encrypted on the Server, and it can be dynamically updated by changing individual coefficients cheaply without redoing the entire setup. Our methods rely on linearly homomorphic encryption and pairings, and our implementation shows good performance for polynomial evaluations with millions of coefficients, and efficient DPoR with terabytes of data. For instance, for a 1TB database, compared to the state of art, we can reduce the Client storage by 5000x, communication size by 20x, and client-side audit time by 2x, at the cost of one order of magnitude increase in server-side audit time.

Proof of Retrievability (PoR) and Provable Data Possession (PDP) schemes have been proposed to ensure the integrity of stored data on untrusted servers. A successful PoR audit ensures, with high probability, that every piece of stored data is recoverable by the server. Most PoR schemes proposed have focused on bandwidth and computation cost, but in some deployment scenarios the size of remote storage can be the most expensive factor. We propose a simple PoR scheme which is a variant on some existing PDP work. Compared to existing audit routines, the server computation cost and bandwidth are higher, but the server storage cost is minimal. Our preliminary work indicates that deploying this scheme may be less costly in commercial cloud settings, depending on the cost structure and frequency of audits.

We tackle the problem of simultaneous transformations of networks represented as graphs. Roughly speaking, one may distinguish two kinds of simultaneous or parallel rewrite relations over complex structures such as graphs: (i) those which transform disjoint subgraphs in parallel and hence can be simulated by successive mere sequential and local transformations and (ii) those which transform overlapping subgraphs simultaneously. In the latter situations, parallel transformations cannot be simulated in general by means of successive local rewrite steps. We investigate this last problem in the framework of overlapping graph transformation systems. As parallel transformation of a graph does not produce a graph in general, we propose first some sufficient conditions that ensure the closure of graphs by parallel rewrite relations. Then we mainly introduce and discuss two parallel rewrite relations over graphs. One relation is functional and thus deterministic, the other one is not functional for which we propose sufficient conditions which ensure its confluence.

We present a layered end-to-end approach for the design and implementation of embedded software on a distributed platform. The approach comprises a high-level modeling and simulation layer (Simulink), a middle-level programming and validation layer (SCADE/Lustre) and a low-level execution layer (TTA). We provide algorithms and tools to pass from one layer to the next. First, a translator from Simulink to Lustre. Second, a set of real-time and code-distribution extensions to Lustre. Third, implementation techniques for decomposing a Lustre program into tasks and messages, scheduling the tasks and messages on the processors and the bus, distributing the Lustre code on the execution platform, and generating the necessary "glue" code.

The goal of this paper is twofold: first a rapid introduction to the concept of hybrid system and second the presentation of a new direction in computer algebra that we have called hybrid computation. Hybrid computation can be seen as the application of the philosophy of hybrid system to the field of computation. We have focused our presentation on four directions that are actually developped in the MASH (Modélisation Algébrique et Systèmes Hybrides) project:Integration of ODE, Dynamic hybrid systems, Generalized splines and Optimal control [5].

Article Solving one and two-dimensional exponential polynomial systems Share on Author: Aude Maignan Department of Mathematics, University of Limoges, France Department of Mathematics, University of Limoges, FranceView Profile Authors Info & Claims ISSAC '98: Proceedings of the 1998 international symposium on Symbolic and algebraic computationAugust 1998 Pages 215–221https://doi.org/10.1145/281508.281616Online:01 August 1998Publication History 5citation408DownloadsMetricsTotal Citations5Total Downloads408Last 12 Months3Last 6 weeks1 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access