Abdessamad Imine

The graph data model is increasingly used in practice due to its flexibility in modeling complex real-life data. However, some security features (e.g., access control) are not receiving sufficient attention from researchers since that graph databases are still in their infancy. Existing access control models do not rise to the finest granularity le...

Social Coding Platforms (SCPs) like GitHub have become central to modern software engineering thanks to their collaborative and version-control features. Like in mainstream Online Social Networks (OSNs) such as Facebook, users of SCPs are subjected to privacy attacks and threats given the high amounts of personal and project-related data available...

Most recommendation systems in social networks provide users with relevant new friend suggestions by processing their personal information or their current friends lists. However, providing such recommendations may leak users’ private information. We present a new differentially private recommendation algorithm that preserves the privacy of both at...

Credit card fraud is becoming a serious and growing problem as a result of the emergence of innovative technologies and communication methods, such as contactless payment. In this article, we present an in-depth review of cutting-edge research on detecting and predicting fraudulent credit card transactions conducted from 2015 to 2021 inclusive. The...

The privacy scoring and privacy settings management mechanisms described in this discourse are early attempts to introduce privacy risk analysis concepts in the area of online social networks (OSNs) from the user perspective. They are also in alignment with the risk-based approach of the EU GDPR toward privacy protection. Privacy scores make users...

As the need to inform OSN users about the privacy risks arising from sharing personal information is being increasingly appreciated, researchers have proposed various methods [5, 6, 8, 9, 15, 39, 95, 112, 116, 117, 132, 137, 147, 148, 150] to compute these risks and to present the result to users in terms of privacy scores.1 The primary aim of thes...

Users may publish various personal data in their OSN profiles, such as their birthday, gender, interests, education, and workplace, in the form of attributes. They can choose appropriate privacy settings, provided by the OSN, to reveal the attributes to suitable audiences such as friends, friends-of-friends, and even strangers who are members of th...

The EU GDPR [56] emphasizes that data subjects should be made aware of the risks related to personal data processing. In general, privacy impact assessment (PIA), whose technical core is referred to as privacy risk analysis (PRA) [45], is used to help service providers understand the privacy risks for data subjects from services they provide. With...

In an OSN, a user forms the first impression on other users by revealing different profile attributes such as his age, gender, interests, and workplace. These attributes constitute the basis of building new friendships as well as reviving and enhancing existing ones. Many studies have documented the relationship between the use of OSNs such as Face...

Privacy settings in OSN profiles allow users to choose the level of visibility of the attributes they reveal. When chosen correctly, the privacy settings of an attribute restricts the data to the intended audience. In Facebook for example, the user can keep an attribute private or reveal it to his friends or friends-of-friends or make it public. So...

The personal data disclosed by users in OSN profiles in terms of attributes can be exploited by other OSN members (e.g., complete strangers, future employers, colleagues, and relatives) to cause various privacy harms such as identity theft, discrimination, or sexual predation for the OSN user.

The privacy settings of the target user and his vicinity contribute to the attributes that are visible about him [39]. Attributes may be visible to a risk source either because they are directly revealed to it by the user or because the risk source can infer their values based on the attributes disclosed by the user’s vicinity.

The EU General Data Protection Regulation (GDPR) recognizes the data subject’s consent as one of the legal grounds for data processing. Targeted advertising, based on personal data processing, is a central source of revenue for data controllers such as Google and Facebook. At present, the implementation of consent mechanisms for such advertisements...

Real-time Collaborative Editors (RCEs) are popular distributed applications that permit large and dynamic groups of collaborators to share and update large multimedia documents across many sites in real time. However, the state-of-the-art models are either locally centralized or globally distributed using a central cloud server to keep shared data...

We present an online attribute inference attack by leveraging Facebook picture metadata (i) alt-text generated by Facebook to describe picture contents, and (ii) comments containing words and emojis posted by other Facebook users. Specifically, we study the correlation of the picture’s owner with Facebook generated alt-text and comments used by com...

Facebook users unknowingly reveal personal information that may help attackers to perpetrate malicious actions. In this paper, we show how sensitive age information of a given target user can be predicted from his/her online pictures. More precisely, we perform age inference attacks by leveraging picture metadata such as (i) alt-texts automatically...

Users in online social networks are vulnerable to attribute inference attacks due to some published data. Thus, the picture owner's gender has a strong influence on individuals' emotional reactions to the photo. In this work, we present a graph-embedding approach for gender inference attacks based on pictures meta-data such as (i) alt-texts generat...

Collaborative editors are one of the most popular collaborative tools. They are being widely used thanks to the success of data sharing platforms where in most of the cases, data is shared with the intent to be edited simultaneously by many users who are distributed and dispersed across the globe. Keeping shared data synchronized is resource-intens...

Social media such as Facebook provides a new way to connect, interact and learn. Facebook allows users to share photos and express their feelings by using comments. However, its users are vulnerable to attribute inference attacks where an attacker intends to guess private attributes (e.g., gender, age, political view) of target users through their...

The EU General Data Protection Regulation (GDPR) recognizes data subject’s consent as a legitimate ground of data processing. At present, consent mechanisms in OSNs are either non-existent or not GDPR compliant. While the absence of consent means a lack of control of the OSN user (data subject) on his personal data, non-compliant consent mechanisms...

To increase awareness about privacy threats, we have designed a tool, SONSAI, for Facebook users to audit their own profiles. SONSAI predicts values of sensitive attributes by machine learning and identifies user public attributes that have guided the learning algorithm towards these sensitive attribute values. Here, we present new aspects of the s...

Online Social Network (OSN) profiles help users to create first impressions on other users and therefore lead to various social benefits. However, users can become the victims of privacy harms such as identity theft, stalking or discrimination due to the personal data revealed in these profiles. So they have to carefully select the privacy settings...

The social benefit derived from online social networks (OSNs) can lure users to reveal unprecedented volumes of personal data to a social graph that is much less trustworthy than the offline social circle. Although OSNs provide users privacy configuration settings to protect their data, these settings are not sufficient to prevent all situations of...

This book constitutes revised selected papers from the 10th International Symposium on Foundations and Practice of Security, FPS 2017, held in Nancy, France in October 2017. The 20 papers presented in this volume were carefully reviewed and selected from 53 submissions. The papers were organized in topical sections named: access control; formal ver...

As the world is progressing quickly towards more connected mobile devices, the use of mobile collaborative applications is gaining an increasing popularity. For instance, real-time data streams and web applications (such as social networking and ad-hoc collaboration) are seamlessly incorporated in mobile applications. Despite this powerful evolutio...

In order to demonstrate privacy threats in social networks we show how to infer user preferences by random walks in a multiple graph representing simultaneously attributes and relationships links. For the approach to scale in a first phase we reduce the space of attribute values by partition in balanced homogeneous clusters. Following the Deepwalk...

While online social networks have become an important channel for social interactions, they also raise ethical and privacy issues. A well known fact is that social networks leak information, that may be sensitive, about users. However, performing accurate real world online privacy attacks in a reasonable time frame remains a challenging task. In th...

The problem of private publication of graph data has attracted a lot of attention recently. The prevalence of differential privacy makes the problem more promising. However, the problem is very challenging because of the huge output space of noisy graphs, up to 2^{n(n-1)/2}. In addition, a large body of existing schemes on differentially private re...

Nowadays, we assist to an explosion of mobile applications due to the rapid development of mobile devices, which are becoming the device of choice for people to collaborate with family members, friends and business colleagues and/or customers. Mobile devices (such as smartphones, tablets and laptops) are well-suited for information delivery than so...

Currently, most of the online social networks (OSN) keep their data secret and in centralized manner. Researchers are allowed to crawl the underlying social graphs (and data) but with limited rates, leading to only partial views of the true social graphs. To overcome this constraint, we may start from user perspective, the contributors of the OSNs....

Complex networks usually expose community structure with groups of nodes sharing many links with the other nodes in the same group and relatively few with the nodes of the rest. This feature captures valuable information about the organization and even the evolution of the network. Over the last decade, a great number of algorithms for community de...

Complex networks usually expose community structure with groups of nodes sharing many links with the other nodes in the same group and relatively few with the nodes of the rest. This feature captures valuable information about the organization and even the evolution of the network. Over the last decade, a great number of algorithms for community de...

Operational Transformation (OT) is a coordination approach used for supporting optimistic replication in distributed collaborative applications, where many users cooperatively manipulate replicated shared objects such as textual or multimedia documents. It allows users to concurrently update the shared data and exchange their updates in any order s...

As the world is progressing quickly towards more connected mobile devices, the use of mobile collaborative applications is gaining an increasing popularity. For instance, real-time data streams and web applications (such as social networking and ad-hoc collaboration) are seamlessly incorporated in mobile applications. Despite this powerful evolutio...

Mobile devices have experienced a huge progress in the capacity of computing, storage and data visualization. They are becoming the device of choice for operating a large variety of applications while supporting real-time collaboration of people and their mobility. Despite this progress, the energy consumption and the network coverage remain a seri...

Undoing operations is an indispensable feature for many collaborative applications, mainly collaborative editors. It provides the ability to restore a correct state of shared data after erroneous operations. In particular, selective undo allows to undo any operation and is based on rearranging operations in the history thanks to the Operational Tra...

Well defined concurrent replicated data structure is very important to design collaborative editing system, particularly, certain properties like out-of-order execution of concurrent operations and data convergence. In this paper, we introduce novel linear data structure based on unique identifier scheme required for indexed communication. These id...

We study the problem of querying virtual security views of XML data that has received a great attention during the past years. A major concern here is that user XPath queries posed on recursive views cannot be rewritten to be evaluated on the underlying XML data. Existing rewriting solutions are based on the non-standard language, “Regular XPath”,...

Mobile devices have experienced a huge progress in computing capacity, storage and visualization of data. They are becoming the device of choice for operating a large variety of applications while supporting real-time collaboration of people and their mobility. Despite this progress, the energy consumption and the network coverage remain a serious...

The powerful evolution of hardware, software and data connectivity of mobile devices (such as smartphones and tablets) stimulates people to publish and share their personal data (like social network information or sensor readings) independently of spatial and temporal constraints. To do this, the development of an efficient semantic web collaborati...

The problem of private publication of graph data has attracted a lot of attention recently. The prevalence of differential privacy makes the problem more promising. However, a large body of existing works on differentially private release of graphs have not answered the question about the upper bounds of privacy budgets. In this paper, for the firs...

Real-time co-authoring of Linked-Data (LD) on the Web is becoming a challenging problem in the Semantic Web area. LD consists of RDF (Resource Description Framework) graphs. We propose to apply state-of-the art collaborative editing techniques to manage shared RDF graphs and to control the concurrent modifications. In this paper, we present two con...

Nowadays, we assist to an explosion of mobile applications due to the rapid development of smartphones. These smartphones are becoming the device of choice for people to collaborate with family members, friends and business colleagues and/or customers. However, building ad-hoc collaboration around mobile applications requires increasing amounts of...

The operational transformation (OT) approach, used in many collaborative editors, allows a group of users to concurrently update replicas of a shared object and exchange their updates in any order. The basic idea is to transform any received update operation before its execution on a replica of the object. Concretely, OT consists of a centralized/d...

We address the polling problem in social networks where users want to preserve the confidentiality of their votes, obtain the correct final result, and hide, if any, their misbehaviors. Guerraoui et al. [15, 16] recently proposed polling protocols that neither rely on any central authority nor cryptography system. However, these protocols can be de...

Uncertain graphs, a form of uncertain data, have recently attracted a lot of attention as they can represent inherent uncertainty in collected data. The uncertain graphs pose challenges to conventional data processing techniques and open new research directions. Going in the reserve direction, this paper focuses on the problem of anonymizing a dete...

Rather than anonymizing social graphs by generalizing them to super nodes/edges or adding/removing nodes and edges to satisfy given privacy parameters, recent methods exploit the semantics of uncertain graphs to achieve privacy protection of participating entities and their relationship. These techniques anonymize a deterministic graph by convertin...

This position paper first summarizes work done by the first author on location privacy and differential privacy. These techniques will help to solve privacy problems in decentralized mobile social networks, which is the main theme of his PhD research. The paper then briefly reviews the state-of-the-art in privacy-preservation of social graphs and c...

Online social networks are currently experiencing a peak and they resemble real platforms of social conversion and content delivery. Indeed, they are exploited in many ways: from conducting public opinion polls about any political issue to planning big social events for a large public. To securely perform these large-scale computations, current pro...

It is increasingly common to find XML views used to enforce access control as found in many applications and commercial database systems. To overcome the overhead of view materialization and maintenance, XML views are necessarily virtual. With this comes the need for answering XML queries posed over virtual views, by rewriting them into equivalent...

Distributed Collaborative Editors are interactive systems where several and dispersed users edit concurrently shared documents. Generally, these systems rely on data replication and use safe coordination protocol which ensures data consistency even though the users’s updates are executed in any order on different copies. Controlling access in such...

The project summarized in this article aims at developing techniques to support access control in Real-Time Distributed Collaborative Editors (RCE). The ever-increasing role of RCE in academic, industry and society comforts the expansion of data sharing and raises growing concerns about controlling access to this data. Indeed, RCE allow for a human...

The Operational Transformation (OT) approach, used in many collaborative editors, allows a group of users to concurrently update replicas of a shared object and exchange their updates in any order. The basic idea of this approach is to transform any received update operation before its execution on a replica of the object. This transformation aims...

Over the past years several works have proposed access control models for XML data where only read-access rights over non-recursive DTDs are considered. A small number of works have studied the access rights for updates. In this paper, we present a general and expressive model for specifying access control on XML data in the presence of the update...

We tackle the polling problem in social networks where the privacy of exchanged information and user reputation are very critical. Indeed, users want to preserve the confidentiality of their votes and to hide, if any, their misbehaviors. Recent works [7,8] proposed polling protocols based on simple secret sharing scheme and without requiring any ce...

Over the past years several works have proposed access control models for XML data where only read-access rights over non-recursive DTDs are considered. A few amount of works have studied the access rights for updates. In this paper, we present a general model for specifying access control on XML data in the presence of update operations of W3C XQu...

L’approche de transformée opérationnelle (TO) est l'une des meilleurs techniques qui permet de supporter la collaboration dans les environnements mobiles et distribués. Les éditeurs collaborative en temps réel utilisent cette technique pour la réconciliation des données modifiées simultanément par plusieurs utilisateurs. Cependant, l’approche TO ut...

Most state-of-the art approaches for securing XML documents allow users to access data only through authorized views defined by annotating an XML grammar (e.g. DTD) with a collection of XPath expressions. To prevent improper disclosure of confidential information, user queries posed on these views need to be rewritten into equivalent queries on the...

Collaborative applications are relevant programs allowing many users to simultaneously cooperate in order to perform a given task on a shared object. These applications are based on replicating shared objects in order to ensure data availability. The Operational Transformation (OT) approach is used for supporting optimistic replication in these app...

This paper describes the design and implementation of a Decentralized Shared Calendar (abbreviated as DeSCal), a distributed application which provides users a decentralized infrastructure to share their calendar events with selected users in a dynamic group. Although being a distributed application, DeSCal is as responsive as a personal calendar....

The progression of mobile technology in recent years has opened up new issues for the development of mobile applications dedicated to mobile devices such as iPhone, Andoid and Windows Phone. Consequently, the adaptation of existing desktop applications with these devices becomes a necessity. However, this adaptation is a challenging problem as they...

The importance of collaborative systems in real-world applications has grown significantly over the recent years. The majority of new applications are designed in a distributed fashion to meet collaborative work requirements. Among these applications, we focus on Distributed Collaborative Editors (DCE) that provide computer support for modifying si...

The importance of collaborative systems in real-world applications has grown significantly over the recent years. The majority of new applications are designed in a distributed fashion to meet collaborative work requirements. Among these applications, we focus on Distributed Collaborative Editors (DCE) that provide computer support for modifying si...

The mobile phone technologies are becoming pervasive in recent years. These items such as IPhones, IPad and Androïds are very attractive since they provide relatively good resources for a mobile device. Several works aim at integrating desktop applications in these tools to make them closer to the real computer. However, adapting desktop applicatio...

The Operational Transformation (OT) approach, used in many collaborative editors, allows a group of users to concurrently update replicas of a shared object and exchange their updates in any order. The basic idea of this approach is to transform any received update operation before its execution on a replica of the object. This transformation aims...

Due to the large size and complex structure of modern networks, firewall policies can contain several thousand rules. The size and complexity of these policies require automated tools providing a user-friendly environment to specify, configure and safely deploy a target policy. When activated in online mode, a firewall policy deployment is a very d...

A collaborative object represents a data type (such as a text document) designed to be shared by a group of dispersed users. The Operational Transformation (OT) is a coordination approach used for supporting optimistic replication for these objects. It allows the users to concurrently update the shared data and exchange their updates in any order s...

A collaborative object represents a data type (such as a text document) designed to be shared by a group of dispersed users. The Operational Transformation (OT) is a coordination approach used for supporting optimistic replication for these objects. It allows the users to concurrently update the shared data and exchange their updates in any order s...

When adding access control layer to a replication based Distributed Collaborative Editor (DCE), ensuring convergence to the same copy of the shared document becomes a challenging problem. We consider here an optimistic access control in the sense that temporarily access right violation is tolerated [3]. This leads to data divergence. To maintain co...

Distributed Collaborative Editors (DCE) provide computer support for modifying simultaneously shared documents, such as articles, wiki pages and programming source code, by dispersed users. Controlling access in such systems is still a challenging problem, as they need dynamic access changes and low latency access to shared documents. In this paper...

In this article, we propose a multi-agent based mobile agent to design an editor that uses the collaborative approach to operational transformed as a method of optimization for the reconciliation of divergent data in mobile and P2P environments. This system allows the location of staff and communication between them in the mobile and P2P environmen...

Collaborative editors consist of a group of users editing a shared document. The Operational Transformation (OT) approach is used for supporting optimistic replication in these editors. It allows the users to concurrently update the shared data and exchange their updates in any order since the convergence of all replicas, i.e. the fact that all use...

Real-time Collaborative Editors (RCE) are a class of distributed systems based on the interaction of several users trying to edit simultaneously shared documents, such as articles, wiki pages and programming source code. Operational Transformation (OT) is considered as the efficient and safe method for consistency maintenance in the literature of c...

Distributed Collaborative Editors (DCE) provide computer support for modifying simultaneously shared documents, such as articles, wiki pages and programming source code, by dispersed users. Controlling access in such systems is still a challenging problem, as they need dynamic access changes and low latency access to shared documents. In this paper...

Real-time collaborative editors (RCE) provide computer support for modifying simultaneously shared documents, such as articles, wiki pages and programming source code, by dispersed users. Due to data replication, operational transformation (OT) is considered as the efficient and safe method for consistency maintenance in the literature of collabora...