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Auditing sumqueries to make a statistical database secure
 ACM TRANS. INF. SYST. SECUR
, 2006
"... In response to queries asked to a statistical database, the query system should avoid releasing summary statistics that could lead to the disclosure of confidential individual data. Attacks to the security of a statistical database may be direct or indirect, and in order to repel them, the query sy ..."
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Cited by 9 (3 self)
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In response to queries asked to a statistical database, the query system should avoid releasing summary statistics that could lead to the disclosure of confidential individual data. Attacks to the security of a statistical database may be direct or indirect, and in order to repel them, the query system should audit queries by controlling the amount of information released by their responses. The paper focuses on sumqueries with a response variable of nonnegative real type and proposes a compact representation of answered sumqueries, called an information model in “normal form”, which allows the query system to decide whether the value of a new sumquery can or cannot be safely answered. If it cannot, then the query system will issue the range of feasible values of the new sumquery consistent with previously answered sumqueries. Both the management of the information model and the answering procedure require solving linearprogramming problems and, since standard linearprogramming algorithms are not polynomially bounded (despite their good performances in practice), effective procedures that make a parsimonious use of them are stated for the general case. Moreover, in the special case that the information model is “graphical”, then it is shown that the answering procedure can be implemented in polynomial time.
Minimal invariant sets in a vertexweighted graph
 THEORETICAL COMPUTER SCIENCE
, 2006
"... A weighting of vertices of a graph is admissible if there exists an edge weighting such that the weight of each vertex equals the sum of weights of its incident edges. Given an admissible vertex weighting of a graph, an invariant set is an edge set such that the sum of the weights of its edges is th ..."
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Cited by 2 (2 self)
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A weighting of vertices of a graph is admissible if there exists an edge weighting such that the weight of each vertex equals the sum of weights of its incident edges. Given an admissible vertex weighting of a graph, an invariant set is an edge set such that the sum of the weights of its edges is the same for every edge weighting, and a nonempty invariant set is minimal if none of its nonempty proper subsets is an invariant set. It is easily seen that every nonempty invariant set is a disjoint union of minimal invariant sets. A graphical characterisation of minimal invariant sets in a bipartite graph is known both in the case the vertex weights are reals and in the case the vertex weights are nonnegative reals. We shall state a graphical characterisation of minimal invariant sets in an arbitrary vertexweighted graph. Moreover, we give a linear algorithm to test an invariant set for minimality. Finally, we state a complete axiomatisation of invariant sets and give a polynomial algorithm to find a set of minimal invariant sets that completely characterise the set of all invariant sets.
Privacy preserving and data mining in an online statistical database of additive type
 PROC. INTERNATIONAL CONFERENCE ON “PRIVACY IN STATISTICAL DATABASES
, 2004
"... In an online statistical database, the queryanswering system should prevent answers to statistical queries from leading to disclosure of confidential data. On the other hand, a statistical user is inclined to data mining, that is, to disclose pieces of information that are implicit in the (explic ..."
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Cited by 1 (1 self)
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In an online statistical database, the queryanswering system should prevent answers to statistical queries from leading to disclosure of confidential data. On the other hand, a statistical user is inclined to data mining, that is, to disclose pieces of information that are implicit in the (explicit) answers to his queries. A key task for both is to find data that is derivable from given summary statistics. We show that this task is easy if data is additive and the set of given summary statistics can be modelled by a graph.
Finding a Nonempty Algebraic Subset of an Edge Set in Linear Time
, 2005
"... A set of edges of a hypergraph H is an algebraic set if its characteristic vector can be expressed as a linear combination of rows of the (nodeedge) incidence matrix of H. Recently it was proven that deciding whether or not a given edgeset of H contains a nonempty algebraic set is an NPcomplete p ..."
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A set of edges of a hypergraph H is an algebraic set if its characteristic vector can be expressed as a linear combination of rows of the (nodeedge) incidence matrix of H. Recently it was proven that deciding whether or not a given edgeset of H contains a nonempty algebraic set is an NPcomplete problem. In this paper we give a linear time algorithm to decide if a given edgeset contains a nonempty algebraic set when the hypergraph is a graph.
Abstract ARTICLE IN PRESS
, 2007
"... www.elsevier.com/locate/tcs An analytical approach to the inference of summary data of additive type ..."
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www.elsevier.com/locate/tcs An analytical approach to the inference of summary data of additive type
Statistical Database Security under . . .
, 2003
"... In a statistical database, the queryanswering system should leave unanswered sumqueries that could lead to the disclosure of confidential data. To this end, each sumquery and previously answered sumqueries should be audited. We give a general framework for controlling the amount of information ..."
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In a statistical database, the queryanswering system should leave unanswered sumqueries that could lead to the disclosure of confidential data. To this end, each sumquery and previously answered sumqueries should be audited. We give a general framework for controlling the amount of information released when sumqueries are answered, both from the viewpoint of the user and from the viewpoint of the queryanswering system. Moreover, we show that, under a suitable queryoverlap restriction, an auditing procedure can be efficiently worked out using flownetwork computation.