254,226 research outputs found
Identifying Security-Critical Cyber-Physical Components in Industrial Control Systems
In recent years, Industrial Control Systems (ICS) have become an appealing
target for cyber attacks, having massive destructive consequences. Security
metrics are therefore essential to assess their security posture. In this
paper, we present a novel ICS security metric based on AND/OR graphs that
represent cyber-physical dependencies among network components. Our metric is
able to efficiently identify sets of critical cyber-physical components, with
minimal cost for an attacker, such that if compromised, the system would enter
into a non-operational state. We address this problem by efficiently
transforming the input AND/OR graph-based model into a weighted logical formula
that is then used to build and solve a Weighted Partial MAX-SAT problem. Our
tool, META4ICS, leverages state-of-the-art techniques from the field of logical
satisfiability optimisation in order to achieve efficient computation times.
Our experimental results indicate that the proposed security metric can
efficiently scale to networks with thousands of nodes and be computed in
seconds. In addition, we present a case study where we have used our system to
analyse the security posture of a realistic water transport network. We discuss
our findings on the plant as well as further security applications of our
metric.Comment: Keywords: Security metrics, industrial control systems,
cyber-physical systems, AND-OR graphs, MAX-SAT resolutio
Extensions of Barrier Sets to Nonzero Roots of the Matching Polynomials
In matching theory, barrier sets (also known as Tutte sets) have been studied
extensively due to its connection to maximum matchings in a graph. In this
paper, we first define -barrier sets. Our definition of a
-barrier set is slightly different from that of a barrier set. However
we show that -barrier sets and barrier sets have similar properties. In
particular, we prove a generalized Berge's Formula and give a characterization
for the set of all -special vertices in a graph
On Representation of the Reeb Graph as a Sub-Complex of Manifold
The Reeb graph is one of the fundamental invariants of a
smooth function with isolated critical points. It is
defined as the quotient space of the closed manifold by a
relation that depends on . Here we construct a -dimensional complex
embedded into which is homotopy equivalent to .
As a consequence we show that for every function on a manifold with finite
fundamental group, the Reeb graph of is a tree. If is an abelian
group, or more general, a discrete amenable group, then
contains at most one loop. Finally we prove that the number of loops in the
Reeb graph of every function on a surface is estimated from above by ,
the genus of .Comment: 18 page
Foliations of Isonergy Surfaces and Singularities of Curves
It is well known that changes in the Liouville foliations of the isoenergy
surfaces of an integrable system imply that the bifurcation set has
singularities at the corresponding energy level. We formulate certain
genericity assumptions for two degrees of freedom integrable systems and we
prove the opposite statement: the essential critical points of the bifurcation
set appear only if the Liouville foliations of the isoenergy surfaces change at
the corresponding energy levels. Along the proof, we give full classification
of the structure of the isoenergy surfaces near the critical set under our
genericity assumptions and we give their complete list using Fomenko graphs.
This may be viewed as a step towards completing the Smale program for relating
the energy surfaces foliation structure to singularities of the momentum
mappings for non-degenerate integrable two degrees of freedom systems.Comment: 30 pages, 19 figure
Surface bundles with genus two Heegaard splittings
It is known that there are surface bundles of arbitrarily high genus which
have genus two Heegaard splittings. The simplest examples are Seifert fibered
spaces with the sphere as a base space, three exceptional fibers and which
allow horizontal surfaces. We characterize the monodromy maps of all surface
bundles with genus two Heegaard splittings and show that each is the result of
integral Dehn surgery in one of these Seifert fibered spaces along loops where
the Heegaard surface intersects a horizontal surface. (This type of surgery
preserves both the bundle structure and the Heegaard splitting.)Comment: 30 pages, 8 figure
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