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50
A First Step towards Automated Detection of Buffer Overrun Vulnerabilities
 In Network and Distributed System Security Symposium
, 2000
"... We describe a new technique for finding potential buffer overrun vulnerabilities in securitycritical C code. The key to success is to use static analysis: we formulate detection of buffer overruns as an integer range analysis problem. One major advantage of static analysis is that security bugs can ..."
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Cited by 339 (10 self)
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We describe a new technique for finding potential buffer overrun vulnerabilities in securitycritical C code. The key to success is to use static analysis: we formulate detection of buffer overruns as an integer range analysis problem. One major advantage of static analysis is that security bugs can be eliminated before code is deployed. We have implemented our design and used our prototype to find new remotelyexploitable vulnerabilities in a large, widely deployed software package. An earlier hand audit missed these bugs. 1.
Complexity and Algorithms for Reasoning About Time: A GraphTheoretic Approach
, 1992
"... Temporal events are regarded here as intervals on a time line. This paper deals with problems in reasoning about such intervals when the precise topological relationship between them is unknown or only partially specified. This work unifies notions of interval algebras in artificial intelligence ..."
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Cited by 86 (11 self)
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Temporal events are regarded here as intervals on a time line. This paper deals with problems in reasoning about such intervals when the precise topological relationship between them is unknown or only partially specified. This work unifies notions of interval algebras in artificial intelligence with those of interval orders and interval graphs in combinatorics. The satisfiability, minimal labeling, all solutions and all realizations problems are considered for temporal (interval) data. Several versions are investigated by restricting the possible interval relationships yielding different complexity results. We show that even when the temporal data comprises of subsets of relations based on intersection and precedence only, the satisfiability question is NPcomplete. On the positive side, we give efficient algorithms for several restrictions of the problem. In the process, the interval graph sandwich problem is introduced, and is shown to be NPcomplete. This problem is als...
Local and global relational consistency
 THEORETICAL COMPUTER SCIENCE
, 1997
"... Local consistency has proven to be an important concept in the theory and practice of constraint networks. In this paper, we present a new definition of local consistency, called relational consistency. The new definition is relationbased, in contrast with the previous definition of local consiste ..."
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Cited by 61 (15 self)
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Local consistency has proven to be an important concept in the theory and practice of constraint networks. In this paper, we present a new definition of local consistency, called relational consistency. The new definition is relationbased, in contrast with the previous definition of local consistency, which we characterize as variablebased. We show the conceptual power of the new definition by showing how it unifies known elimination operators such as resolution in theorem proving, joins in relational databases, and variable elimination for solving linear inequalities. Algorithms for enforcing various levels of relational consistency are introduced and analyzed. We also show the usefulness of the new definition in characterizing relationships between properties of constraint networks and the level of local consistency needed to ensure global consistency.
Tight Bounds and 2Approximation Algorithms for Integer Programs with Two Variables per Inequality
 Mathematical Programming
, 1992
"... . The problem of integer programming in bounded variables, over constraints with no more than two variables in each constraint is NPcomplete, even when all variables are binary. This paper deals with integer linear minimization problems in n variables subject to m linear constraints with at most tw ..."
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Cited by 41 (5 self)
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. The problem of integer programming in bounded variables, over constraints with no more than two variables in each constraint is NPcomplete, even when all variables are binary. This paper deals with integer linear minimization problems in n variables subject to m linear constraints with at most two variables per inequality, and with all variables bounded between 0 and U . For such systems, a 2\Gammaapproximation algorithm is presented that runs in time O(mnU 2 log(Un 2 =m)), so it is polynomial in the input size if the upper bound U is polynomially bounded. The algorithm works by finding first a superoptimal feasible solution that consists of integer multiples of 1 2 . That solution gives a tight bound on the value of the minimum. It further more has an identifiable subset of integer components that retain their value in an integer optimal solution of the problem. These properties are a generalization of the properties of the vertex cover problem. The algorithm described is, ...
Approximating Clique and Biclique Problems
 J. Algorithms
, 1998
"... We present here 2approximation algorithms for several node deletion and edge deletion biclique problems and for an edge deletion clique problem. The biclique problem is to find a node induced subgraph which is bipartite and complete. The objective is to minimize the total weight of nodes or edges d ..."
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Cited by 37 (1 self)
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We present here 2approximation algorithms for several node deletion and edge deletion biclique problems and for an edge deletion clique problem. The biclique problem is to find a node induced subgraph which is bipartite and complete. The objective is to minimize the total weight of nodes or edges deleted so that the remaining subgraph is bipartite complete. Several variants of the biclique problem are studied here where the problem is defined on bipartite graph or on general graphs with or without the requirement that each side of the bipartition forms an independent set. The maximum clique problem is formulated as maximizing the number (or weight) of edges in the complete subgraph. A 2approximation algorithm is given for the minimum edge deletion version of this problem. The approximation algorithms given here are derived as a special case of an approximation technique devised for a class of formulations introduced by Hochbaum [Hoc96]. All approximation algorithms described (and the...
Two Variables per Linear Inequality as an Abstract Domain
 Logicbased Program Synthesis and Transformation, volume 2664 of LNCS
, 2003
"... Abstract. This paper explores the spatial domain of sets of inequalities where each inequality contains at most two variables – a domain that is richer than intervals and more tractable than general polyhedra. We present a complete suite of efficient domain operations for linear systems with two var ..."
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Cited by 33 (9 self)
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Abstract. This paper explores the spatial domain of sets of inequalities where each inequality contains at most two variables – a domain that is richer than intervals and more tractable than general polyhedra. We present a complete suite of efficient domain operations for linear systems with two variables per inequality with unrestricted coefficients. We exploit a tactic in which a system of inequalities with at most two variables per inequality is decomposed into a series of projections – one for each two dimensional plane. The decomposition enables all domain operations required for abstract interpretation to be expressed in terms of the two dimensional case. The resulting operations are efficient and include a novel planar convex hull algorithm. Empirical evidence suggests that widening can be applied effectively, ensuring tractability. 1
A Unit Two Variable Per Inequality Integer Constraint Solver for Constraint Logic Programming
 In Proceedings of the Twentieth Australasian Computer Science Conference
, 1995
"... One of the problems with the traditional finite domains approach to solving integer problems in a constraint logic programming context is that all variables require explicit bounds. If no explicit bounds are available then the finite domain solver can be very inefficient on certain classes of proble ..."
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Cited by 23 (3 self)
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One of the problems with the traditional finite domains approach to solving integer problems in a constraint logic programming context is that all variables require explicit bounds. If no explicit bounds are available then the finite domain solver can be very inefficient on certain classes of problem. We present an alternative approach to solving integer constraints based on a polynomialtime solver for a restricted class of integer constraints. This approach does not require bounds information, avoids bad behaviour for a larger class of problems, and is competitive with bounds propagation for the types of problem examined. We give a detailed description of the implementation of the core solver, discuss how it can be used to as the basis of a more general solver, and present some computational results. 1 Introduction Integer constraints are an important class used to represent many forms of problems of practical interest. For example scheduling, resource allocation and route plannin...
Constraint Query Algebras
 Constraints Journal
, 1996
"... . Constraint query languages are natural extensions of relational database query languages. A framework for their declarative specification (constraint calculi) and efficient implementation (low data complexity and secondary storage indexing) was presented in Kanellakis et al., 1995. Constraint quer ..."
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Cited by 19 (5 self)
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. Constraint query languages are natural extensions of relational database query languages. A framework for their declarative specification (constraint calculi) and efficient implementation (low data complexity and secondary storage indexing) was presented in Kanellakis et al., 1995. Constraint query algebras form a procedural language layer between highlevel declarative calculi and lowlevel indexing methods. Just like the relational algebra, this intermediate layer can be very useful for program optimization. In this paper, we study properties of constraint query algebras, which we present through three concrete examples. The dense order constraint algebra illustrates how the appropriate canonical form can simplify expensive operations, such as projection, and facilitate interaction with updates. The monotone twovariable linear constraint algebra illustrates the concept of strongly polynomial operations. Finally, the lazy evaluation of (non)linear constraint algebras illustrates ho...
Fast and simple approximation schemes for generalized flow
 Math. Program., Ser. A
, 2001
"... We present fast and simple fully... ..."