Olivier Raynaud - Academia.edu (original) (raw)

Papers by Olivier Raynaud

Research paper thumbnail of A Tool for Classification of Sequential Data

European Conference on Artificial Intelligence, 2016

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Research paper thumbnail of A Closure Algorithm Using a Recursive Decomposition of the Set of Moore Co-families

Given a set Un = {1,..,n}, a collection M of subsets of Un that is closed under intersection and ... more Given a set Un = {1,..,n}, a collection M of subsets of Un that is closed under intersection and contains Un is known as a Moore family. The set of Moore families for a fixed n is in bijection with the set of Moore co-families (union-closed families containing the empty set) denoted itself Mn. This paper follows the work initiated in [7] and [8] about the recursive decomposition of the lattice of Moore co-families. We first show that each Moore co-family can be represented by a decomposition tree and we use this principle to design an original algorithm to close under union any given family. Then we discuss about the time complexity and give some experimental results.

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Research paper thumbnail of Semantic Mediation for A Posteriori Log Analysis

Proceedings of the 14th International Conference on Availability, Reliability and Security, 2019

The a posteriori access control mode consists in monitoring actions performed by users, to detect... more The a posteriori access control mode consists in monitoring actions performed by users, to detect possible violations of the security policy and to apply sanctions or reparations. In general, logs are among the first data sources that information security specialists consult for forensics when they suspect that something went wrong. One difficult challenge we face when analyzing logs, is the multiple log file formats. However, normalizing logs in one format needs a lot of processing especially because log files usually contain a high volume of data. Our study proposes then to tackle this problem, by leaving the different log formats as they are, and retrieving information from logs by querying them. A semantic mediator makes it possible to inter-operate various sources of information without modifying their internal functioning. It can be responsible for locating data sources, to transmit queries to each source, or from one source to another, to retrieve the queries responses and po...

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Research paper thumbnail of A Posteriori Access Control with an Administrative Policy

Advances in Security, Networks, and Internet of Things

The a posteriori access control is a particular type of access control in which security auditors... more The a posteriori access control is a particular type of access control in which security auditors tend to verify policy compliance by analyzing logs. However, in this type of access control, the investigations are done after the occurrence of a log event. Therefore, the rules defined in the security policy might not be the same as the ones that were at the time of the access. Furthermore, administrators should have the right privileges to perform a modification on the security policy, and these privileges might be altered over time as well. This chapter treats the a posteriori access control in case of an evolving policy. It proposes an approach, based on the Event Calculus, that consists in getting the security rules that were in place at the time of the access, as well as monitoring administrators’ actions since themselves can be held accountable.

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Research paper thumbnail of An Incremental Algorithm for Computing n-Dimensional Concepts

The problem of computing maximal rectangles (concepts) from a binary relation (context) has recei... more The problem of computing maximal rectangles (concepts) from a binary relation (context) has received much attention. The same cannot be said of the general, n-dimensional case. In this work, we propose the first output-polynomial incremental algorithm for computing the n-concepts of an n-context.

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Research paper thumbnail of A Posteriori Analysis of Policy Temporal Compliance

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Research paper thumbnail of Algorithms for a Bit-Vector Encoding of Trees

A bit-vector encoding is a well known method for representing hierarchies (i.e. partially ordered... more A bit-vector encoding is a well known method for representing hierarchies (i.e. partially ordered sets). This encoding corresponds to an embedding of a given hierarchy into a Boolean lattice whose dimension is the encoding’s size. Computing an optimal bit-vector encoding, which size is called the 2-dimension, is an \(\mathcal {N}\mathcal {P}\)-hard problem. Hence, many algorithms were designed to provide good bit-vector encoding. In this paper, we study tree hierarchies. We analyse previous algorithms for their bit-vector encoding then we point out their common strategy that led us to design a new algorithm improving all the previous ones.

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Research paper thumbnail of Accountability in the A Posteriori Access Control: A Requirement and a Mechanism

The a posteriori access control is a flexible type of access control in which policy violations a... more The a posteriori access control is a flexible type of access control in which policy violations are deterred by applying accountability. However, the definition of the accountability process is frequently underestimated, as the auditors usually pay more attention to detecting violations. In this paper, we define accountability as a requirement and as a mechanism to serve the a posteriori access control.

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Research paper thumbnail of Twins Vertices in Hypergraphs

Twin vertices in graphs correspond to vertices sharing the same neighborhood. We propose an exten... more Twin vertices in graphs correspond to vertices sharing the same neighborhood. We propose an extension to hypergraphs of the concept of twin vertices. For this we give two characterizations of twin vertices in hypergraphs, a first one in term of clone vertices (the concept of clone has been introduced in [16]) and a second one in term of committees (introduced in [6]). Finally we give an algorithm to aknowledge a set as committee and two algorithms to compute clone-twin vertices classes ans committee-twin vertices classes.

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Research paper thumbnail of About The Recursive Decomposition of the lattice of co-Moore Families

Given a set Un = {0, 1, ..., n − 1}, a collection M of subsets of Un that is closed under interse... more Given a set Un = {0, 1, ..., n − 1}, a collection M of subsets of Un that is closed under intersection and contains Un is known as a Moore family. The set of Moore families for a fixed n is in bijection with the set of Moore co-families (union-closed families containing the empty set) denoted itself Mn. In this paper, we propose for the first time a recursive definition of the set of Moore co-families on Un. These results follow the work carried out in [1] to enumerate the number of Moore families on U7.

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Research paper thumbnail of Implementing collection of sets with trie: a stepping stone for performances ?

Main operations of the Set Collection Abstract Data Type are insertion, research and deletion. A ... more Main operations of the Set Collection Abstract Data Type are insertion, research and deletion. A well known option to implement these operations is to use hashtable. Although hashtable does not admit good time complexities in the worst case, the practical time complexities are efficient. Another option is to use the data structure known as the trie. The trie is useful for two main reasons. Firstly, with such a data structure, mentionned operations admit very good theoretical time complexities. Secondly a trie can be seen as a compact representation of a collection of sets since some parts of them are merged together. Aim of this article is to evaluate performances of the trie data structure. The Java language proposes an abstract class corresponding to the Set Collection A.D.T. operations. We propose in this article three different implementations of this abstract class. All of them are variations of the way to manage the sons of nodes. Theoretical complexities are then evaluated. A...

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Research paper thumbnail of Algoritmos de conteo de las familias de Moore aplicación al caso n = 7

Boletin De Matematicas, 2009

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Research paper thumbnail of Am I Really Who I Claim to Be?

Advances in Intelligent Systems and Computing, 2015

Faced with both identity theft and the theft of means of authentication, users of digital service... more Faced with both identity theft and the theft of means of authentication, users of digital services are starting to look rather suspiciously at online systems. The behavior is made up of a series of observable actions of an Internet user and, taken as a whole, the most frequent of these actions amount to habit. Habit and reputation offer ways of recognizing the user. The introduction of an implicit means of authentication based upon the users’ behavior allows websites and businesses to rationalize the risks they take when authorizing access to critical functionalities. This rationalization brings with it user trust as a result of increased security.

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Research paper thumbnail of Counting of Moore Families for n=7

Lecture Notes in Computer Science, 2010

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Research paper thumbnail of Using Closed Itemsets for Implicit User Authentication in Web Browsing

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Research paper thumbnail of Interactive Association Rules Discovery

Lecture Notes in Computer Science, 2006

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Research paper thumbnail of Efficient algorithms for clone items detection

CLA'05, 2005

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Research paper thumbnail of A Tool for Classification of Sequential Data

Classification of sequential data (data obtained from series of actions in chronological order) h... more Classification of sequential data (data obtained from series of actions in chronological order) has many applications in security, marketing or ergonomy. In this paper, we present a tool for classification of sequential data. We introduce a new clean dataset of web-browsing logs, and study the case of implicit authentification from web-browsing. We then detail more of the functioning of the tool and some of its parameters.

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Research paper thumbnail of A closed sets based learning classifier for implicit authentication in web browsing

Discrete Applied Mathematics

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Research paper thumbnail of Encoding Partial Orders Through Modular Decomposition

Proceedings of the First EAI International Conference on Computer Science and Engineering, 2017

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Research paper thumbnail of A Tool for Classification of Sequential Data

European Conference on Artificial Intelligence, 2016

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Research paper thumbnail of A Closure Algorithm Using a Recursive Decomposition of the Set of Moore Co-families

Given a set Un = {1,..,n}, a collection M of subsets of Un that is closed under intersection and ... more Given a set Un = {1,..,n}, a collection M of subsets of Un that is closed under intersection and contains Un is known as a Moore family. The set of Moore families for a fixed n is in bijection with the set of Moore co-families (union-closed families containing the empty set) denoted itself Mn. This paper follows the work initiated in [7] and [8] about the recursive decomposition of the lattice of Moore co-families. We first show that each Moore co-family can be represented by a decomposition tree and we use this principle to design an original algorithm to close under union any given family. Then we discuss about the time complexity and give some experimental results.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Semantic Mediation for A Posteriori Log Analysis

Proceedings of the 14th International Conference on Availability, Reliability and Security, 2019

The a posteriori access control mode consists in monitoring actions performed by users, to detect... more The a posteriori access control mode consists in monitoring actions performed by users, to detect possible violations of the security policy and to apply sanctions or reparations. In general, logs are among the first data sources that information security specialists consult for forensics when they suspect that something went wrong. One difficult challenge we face when analyzing logs, is the multiple log file formats. However, normalizing logs in one format needs a lot of processing especially because log files usually contain a high volume of data. Our study proposes then to tackle this problem, by leaving the different log formats as they are, and retrieving information from logs by querying them. A semantic mediator makes it possible to inter-operate various sources of information without modifying their internal functioning. It can be responsible for locating data sources, to transmit queries to each source, or from one source to another, to retrieve the queries responses and po...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A Posteriori Access Control with an Administrative Policy

Advances in Security, Networks, and Internet of Things

The a posteriori access control is a particular type of access control in which security auditors... more The a posteriori access control is a particular type of access control in which security auditors tend to verify policy compliance by analyzing logs. However, in this type of access control, the investigations are done after the occurrence of a log event. Therefore, the rules defined in the security policy might not be the same as the ones that were at the time of the access. Furthermore, administrators should have the right privileges to perform a modification on the security policy, and these privileges might be altered over time as well. This chapter treats the a posteriori access control in case of an evolving policy. It proposes an approach, based on the Event Calculus, that consists in getting the security rules that were in place at the time of the access, as well as monitoring administrators’ actions since themselves can be held accountable.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of An Incremental Algorithm for Computing n-Dimensional Concepts

The problem of computing maximal rectangles (concepts) from a binary relation (context) has recei... more The problem of computing maximal rectangles (concepts) from a binary relation (context) has received much attention. The same cannot be said of the general, n-dimensional case. In this work, we propose the first output-polynomial incremental algorithm for computing the n-concepts of an n-context.

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Research paper thumbnail of A Posteriori Analysis of Policy Temporal Compliance

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Algorithms for a Bit-Vector Encoding of Trees

A bit-vector encoding is a well known method for representing hierarchies (i.e. partially ordered... more A bit-vector encoding is a well known method for representing hierarchies (i.e. partially ordered sets). This encoding corresponds to an embedding of a given hierarchy into a Boolean lattice whose dimension is the encoding’s size. Computing an optimal bit-vector encoding, which size is called the 2-dimension, is an \(\mathcal {N}\mathcal {P}\)-hard problem. Hence, many algorithms were designed to provide good bit-vector encoding. In this paper, we study tree hierarchies. We analyse previous algorithms for their bit-vector encoding then we point out their common strategy that led us to design a new algorithm improving all the previous ones.

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Research paper thumbnail of Accountability in the A Posteriori Access Control: A Requirement and a Mechanism

The a posteriori access control is a flexible type of access control in which policy violations a... more The a posteriori access control is a flexible type of access control in which policy violations are deterred by applying accountability. However, the definition of the accountability process is frequently underestimated, as the auditors usually pay more attention to detecting violations. In this paper, we define accountability as a requirement and as a mechanism to serve the a posteriori access control.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Twins Vertices in Hypergraphs

Twin vertices in graphs correspond to vertices sharing the same neighborhood. We propose an exten... more Twin vertices in graphs correspond to vertices sharing the same neighborhood. We propose an extension to hypergraphs of the concept of twin vertices. For this we give two characterizations of twin vertices in hypergraphs, a first one in term of clone vertices (the concept of clone has been introduced in [16]) and a second one in term of committees (introduced in [6]). Finally we give an algorithm to aknowledge a set as committee and two algorithms to compute clone-twin vertices classes ans committee-twin vertices classes.

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Research paper thumbnail of About The Recursive Decomposition of the lattice of co-Moore Families

Given a set Un = {0, 1, ..., n − 1}, a collection M of subsets of Un that is closed under interse... more Given a set Un = {0, 1, ..., n − 1}, a collection M of subsets of Un that is closed under intersection and contains Un is known as a Moore family. The set of Moore families for a fixed n is in bijection with the set of Moore co-families (union-closed families containing the empty set) denoted itself Mn. In this paper, we propose for the first time a recursive definition of the set of Moore co-families on Un. These results follow the work carried out in [1] to enumerate the number of Moore families on U7.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Implementing collection of sets with trie: a stepping stone for performances ?

Main operations of the Set Collection Abstract Data Type are insertion, research and deletion. A ... more Main operations of the Set Collection Abstract Data Type are insertion, research and deletion. A well known option to implement these operations is to use hashtable. Although hashtable does not admit good time complexities in the worst case, the practical time complexities are efficient. Another option is to use the data structure known as the trie. The trie is useful for two main reasons. Firstly, with such a data structure, mentionned operations admit very good theoretical time complexities. Secondly a trie can be seen as a compact representation of a collection of sets since some parts of them are merged together. Aim of this article is to evaluate performances of the trie data structure. The Java language proposes an abstract class corresponding to the Set Collection A.D.T. operations. We propose in this article three different implementations of this abstract class. All of them are variations of the way to manage the sons of nodes. Theoretical complexities are then evaluated. A...

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Research paper thumbnail of Algoritmos de conteo de las familias de Moore aplicación al caso n = 7

Boletin De Matematicas, 2009

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Am I Really Who I Claim to Be?

Advances in Intelligent Systems and Computing, 2015

Faced with both identity theft and the theft of means of authentication, users of digital service... more Faced with both identity theft and the theft of means of authentication, users of digital services are starting to look rather suspiciously at online systems. The behavior is made up of a series of observable actions of an Internet user and, taken as a whole, the most frequent of these actions amount to habit. Habit and reputation offer ways of recognizing the user. The introduction of an implicit means of authentication based upon the users’ behavior allows websites and businesses to rationalize the risks they take when authorizing access to critical functionalities. This rationalization brings with it user trust as a result of increased security.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Counting of Moore Families for n=7

Lecture Notes in Computer Science, 2010

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Research paper thumbnail of Using Closed Itemsets for Implicit User Authentication in Web Browsing

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Interactive Association Rules Discovery

Lecture Notes in Computer Science, 2006

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Efficient algorithms for clone items detection

CLA'05, 2005

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A Tool for Classification of Sequential Data

Classification of sequential data (data obtained from series of actions in chronological order) h... more Classification of sequential data (data obtained from series of actions in chronological order) has many applications in security, marketing or ergonomy. In this paper, we present a tool for classification of sequential data. We introduce a new clean dataset of web-browsing logs, and study the case of implicit authentification from web-browsing. We then detail more of the functioning of the tool and some of its parameters.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A closed sets based learning classifier for implicit authentication in web browsing

Discrete Applied Mathematics

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Encoding Partial Orders Through Modular Decomposition

Proceedings of the First EAI International Conference on Computer Science and Engineering, 2017

Bookmarks Related papers MentionsView impact