Searching Is Not Jumping

Barrière, Lali; Fraigniaud, Pierre; Santoro, Nicola; Thilikos, Dimitrios M.

doi:10.1007/978-3-540-39890-5_4

Cited by 55 publications

(67 citation statements)

References 14 publications

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“…One of the interesting topics regarding this model of graph searching is the price of connectivity, that is, the ratio of the connected search number and the classical search number. For results and discussions on this issue see, e.g., [3,4,7,17,37]. For surveys on connected graph searching we refer the reader to [1,25].…”

Section: Related Workmentioning

confidence: 99%

Distributed graph searching with a sense of direction

2014

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In this work we consider the edge searching problem for vertex-weighted graphs with arbitrarily fast and invisible fugitive. The weight function ω provides for each vertex v the minimum number of searchers required to guard v, i.e., the fugitive may not pass through v without being detected only if at least ω(v) searchers are present at v. This problem is a generalization of the classical edge searching problem, in which one has ω ≡ 1. We assume that with a graph G to be searched, there is associated a partition (V 1 , . . . , V t ) of its vertex set such that edges are allowed only within each V i and between two consecutive V i 's. We provide an algorithm for distributed monotone connected edge searching of such graphs, where the searchers are initially placed on an arbitrary vertex of G and have no a priori knowledge on G, but they have a sense of direction that lets them recognize whether an edge incident to already explored vertex in V i leads to a vertex in one of V i−1 , V i or V i+1 . Starting from any vertex the algorithm uses at most 3·max i=1,...,t ω(V i )+1 searchers, where ω(V i ) = v∈V i ω(v). We also prove that this algorithm is best possible up to a small additive constant, that is, each distributed searching algorithm in worst case must use 3 · max i=1,...,t ω(V i ) − 1 searchers for some graphs.

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Section: Related Workmentioning

confidence: 99%

Distributed graph searching with a sense of direction

2014

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“…A clean site becomes contaminated if at least one of its neighbors is contaminated. External decontamination has been studied in the context of intruder capture to design algorithms to neutralize a virus in a network, or in graph search (e.g., [3,31,25,6,4]). The main goal of decontamination in these settings is usually to design a strategy that employs the minimum possible size of the team of cleaning agents.…”

Section: Backgrounds and Related Workmentioning

confidence: 99%

A Review of Computation Solutions by Mobile Agents in an Unsafe Environment

Zarrad¹,

Daadaa²

2013

IJACSA

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Abstract-Exploration in an unsafe environment is one of the major problems that can be seen as a basic block for many distributed mobile protocols. In such environment we consider that either the nodes (hosts) or the agents can pose some danger to the network. Two cases are considered. In the first case, the dangerous node is a called black hole, a node where incoming agents are trapped, and the problem is for the agents to locate it. In the second case, the dangerous agent is a virus; an agent moving between nodes infecting them, and the problem is for the "good" agents to capture it, and decontaminate the network.In this paper, we present several solutions for a black-hole and network decontamination problems. Then, we analyze their efficiency. Efficiency is evaluated based on the complexity, and the effort is in the minimization of the number of simultaneous decontaminating elements active in the system while performing the decontamination techniques.

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“…Another approach could consist of considering only the bank network where the travelling cost is added by assigning weights to the edges (where weights represent physical distances), and by letting searchers jump from one node to the other. It is interesting to note that for any non-weighted tree T with n nodes the ratio between the connected search number csn(T ) and the regular search number sn(T ) (i.e., for agents that may jump) is bounded by, csn(T )/sn(T ) ≤ 2 (see [4]), i.e., any optimal connected strategy will require at most twice the number of agents than a non-connected one (at least in the non-weighted case). We thus leave the two above mentioned extensions as a future work and for simplicity, in this work we concentrate on the scenario in which we do not consider the technician motion as a parameter to optimize.…”

Section: Upgrading Vs Decontaminatingmentioning

confidence: 99%

Secure Upgrade of Hardware Security Modules in Bank Networks

Focardi

Luccio

2010

Automated Reasoning for Security Protocol Analysis and Issues in the Theory of Security

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Abstract. We study the secure upgrade of critical components in wide networked systems, focussing on the case study of PIN processing Hardware Security Modules (HSMs). These tamper-resistant devices, used by banks to securely transmit and verify the PIN typed at the ATMs, have been shown to suffer from API level attacks that allow an insider to recover user PINs and, consequently, clone cards. Proposed fixes require to reduce and modify the HSM functionality by, e.g., sticking on a single format of the transmitted PIN or adding MACs for the integrity of user data. Upgrading HSMs worldwide is, of course, unaffordable. We thus propose strategies to incrementally upgrade the network so to obtain upgraded, secure subnets, while preserving the compatibility towards the legacy system. Our strategies aim at finding tradeoffs between the cost for special "guardian" HSMs used on the borderline between secure and insecure nodes, and the size of the team working in the upgrade process, representing the maximum number of nodes that can be simultaneously upgraded.

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Searching Is Not Jumping

Cited by 55 publications

References 14 publications

Distributed graph searching with a sense of direction

Distributed graph searching with a sense of direction

A Review of Computation Solutions by Mobile Agents in an Unsafe Environment

Secure Upgrade of Hardware Security Modules in Bank Networks

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