Decentralized Online Social Networks Research Articles

Information consumption and boundary spanning in Decentralized Online Social Networks: The case of Mastodon users

Decentralized Online Social Networks (DOSNs) represent a growing trend in the social media landscape, as opposed to the well-known centralized peers, which are often in the spotlight due to privacy concerns and a vision typically focused on monetization through user relationships. By exploiting open-source software, DOSNs allow users to create their own servers, or instances, thus favoring the proliferation of platforms that are independent yet interconnected with each other in a transparent way. Nonetheless, the resulting cooperation model, commonly known as the Fediverse, still represents a world to be fully discovered, since existing studies have mainly focused on a limited number of structural aspects of interest in DOSNs.In this work, we aim to fill a lack of study on user relations and roles in DOSNs, by taking two main actions: understanding the impact of decentralization on how users relate to each other within their membership instance and/or across different instances, and unveiling user roles that can explain two interrelated axes of social behavioral phenomena, namely information consumption and boundary spanning. To this purpose, we build our analysis on user networks from Mastodon, since it represents the most widely used DOSN platform. We believe that the findings drawn from our study on Mastodon users’ roles and information flow can pave a way for further development of fascinating research on DOSNs.

Network Analysis of the Information Consumption-Production Dichotomy in Mastodon User Behaviors

Decentralized Online Social Networks (DOSNs) are today an established alternative to the popular centralized counterparts. In this work, we push forward research on user behaviors in a decentralized context, by exploring the dichotomy between information consumption and production. Using the Mastodon user network as a proxy for the Fediverse landscape, we address two main research questions: Do the consumers, resp. producers, identified in one instance exhibit the same behavior consistently while interacting with other instances? and, Are there users who behave as consumers in one instance and simultaneously as producers in other instances, or vice versa? In this respect, our results reveal interesting traits of Mastodon users, yet unveil the emergence for further studies that can embrace other services in the Fediverse.

Bridging separate communities with common interest in distributed social networks through the use of social objects

In light of the growing number of user privacy violationsin centralized social networks, the need to define effective platforms for decentralized online social networks (DOSNs) is deeply felt. Interesting solutions have been proposed in the past, which own the necessary mechanisms to allow users keeping control over their personal information and setting the rules to regulate the access of other users. Unfortunately, the effectiveness of this type of solutions is severely reduced by the fact that different user communities with a shared interest could be disconnected/separated from each other. This translates into a reduced ability in effectively spreading data of common interest towards all interested users, as it currently happens in centralized social networks. In order to overcome the cited limitation, this paper proposes a disruptive approach, which exploits the availability of a new class of Internet of Things (IoT) devices with autonomous social behaviors and cognitive abilities. Such devices can be leveraged as friendship intermediaries between devices’ owners who are connected to a DOSN platform and share the same interest. We will demonstrate that clear advantages can be achieved in terms of increased percentage of Interested Reachable Nodes (a specific measure of Delivery Ratio) in distributed social networks among humans, when enhanced with so called Mediator Objects adhering to the well-known social IoT (SIoT) paradigm.

Understanding the growth of the Fediverse through the lens of Mastodon

Open-source, Decentralized Online Social Networks (DOSNs) are emerging as alternatives to the popular yet centralized and profit-driven platforms like Facebook or Twitter. In DOSNs, users can set up their own server, or instance, while they can actually interact with users of other instances. Moreover, by adopting the same communication protocol, DOSNs become part of a massive social network, namely the Fediverse. Mastodon is the most relevant platform in the Fediverse to date, and also the one that has attracted attention from the research community. Existing studies are however limited to an analysis of a relatively outdated sample of Mastodon focusing on few aspects at a user level, while several open questions have not been answered yet, especially at the instance level. In this work, we aim at pushing forward our understanding of the Fediverse by leveraging the primary role of Mastodon therein. Our first contribution is the building of an up-to-date and highly representative dataset of Mastodon. Upon this new data, we have defined a network model over Mastodon instances and exploited it to investigate three major aspects: the structural features of the Mastodon network of instances from a macroscopic as well as a mesoscopic perspective, to unveil the distinguishing traits of the underlying federative mechanism; the backbone of the network, to discover the essential interrelations between the instances; and the growth of Mastodon, to understand how the shape of the instance network has evolved during the last few years, also when broading the scope to account for instances belonging to other platforms. Our extensive analysis of the above aspects has provided a number of findings that reveal distinguishing features of Mastodon and that can be used as a starting point for the discovery of all the DOSN Fediverse.

A Graph-Based Socioeconomic Analysis of Steemit

Online social networks (OSNs) have changed the way of how people interact; however, lately, people are questioning more and more their business models. During the last ten years, new solutions based on decentralized architectures have been proposed, namely, decentralized OSNs (DOSNs) and blockchain online social medias (BOSMs). DOSNs were introduced several years ago and their main goal is the preservation of the privacy of the users in such a way that the data and the content of a user are always under their control. BOSMs leverage the usage of blockchain either to enforce the privacy of the users or to redistribute the wealth generated by the platform through a rewarding system. Steemit is the most stable and well-known BOSM with more than 1 million registered users, where users can create their own social network by following other users. To the best of our knowledge, no study exists on the relationship between the economic and social characteristics of BOSMs and on the way the rewarding system affects the social activity. The main goal of this article is to evaluate the characteristics of the Steemit follower-following graph to understand how the social and the economic aspects of BOSMs intertwine and influence each other. We study the properties of the Steemit follower-following graph and a few selected hotspot contents. The analysis shows that users are highly encouraged to be socially active, especially producing content, but the richest users are not also the most social ones, which suggests us that users can get rich without much involvement in the platform, using external mechanisms.

Blockchain-based access control management for Decentralized Online Social Networks

Online Social Networks (OSNs) represent today a big communication channel where users spend a lot of time to share personal data. Unfortunately, the big popularity of OSNs can be compared with their big privacy issues. Indeed, several recent scandals have demonstrated their vulnerability. Decentralized Online Social Networks (DOSNs) have been proposed as an alternative solution to the current centralized OSNs. DOSNs do not have a service provider that acts as central authority and users have more control over their information. Several DOSNs have been proposed during the last years. However, the decentralization of the social services requires efficient distributed solutions for protecting the privacy of users. During the last years the blockchain technology has been applied to Social Networks in order to overcome the privacy issues and to offer a real solution to the privacy issues in a decentralized system. However, in these platforms the blockchain is usually used as a storage, and content is public. In this paper, we propose a manageable and auditable access control framework for DOSNs using blockchain technology for the definition of privacy policies. The resource owner uses the public key of the subject to define auditable access control policies using Access Control List (ACL), while the private key associated with the subject’s Ethereum account is used to decrypt the private data once access permission is validated on the blockchain. We provide an evaluation of our approach by exploiting the Rinkeby Ethereum testnet to deploy the smart contracts. Experimental results clearly show that our proposed ACL-based access control outperforms the Attribute-based access control (ABAC) in terms of gas cost. Indeed, a simple ABAC evaluation function requires 280,000 gas, instead our scheme requires 61,648 gas to evaluate ACL rules.

The Contextual Ego Network P2P Overlay for the Next Generation Social Networks

Internet has completely evolved in recent years, and smart devices, such as mobile and IoT devices have become pervasive in the daily life of people. Internet is becoming more social, and Online Social Networking platforms (OSNs) have become part of the real life of people. Current Online Social Media platforms are centralized. Centralization presents several drawbacks, and during the last years several privacy issues have been arisen concerning the control of private data. Indeed, those platforms offer inadequate guarantees where it concerns the privacy of their users. These problems have been confronted by exploiting decentralized solutions. Decentralized Online Social Networks (DOSNs) guarantee more control over private data. Thanks to the definition of a Next Generation Internet focused on people, the need for a new generation of Decentralized Online Social Networks, which puts the user at the center of the system, has been arisen. The HELIOS project tackles this issue by introducing a new decentralized paradigm. In this paper, we present the Contextual Ego Network (CEN), a new P2P Social Overlay built by exploiting the real life of users. We propose a formal definition of the structure, the implementation of the structure in a Java library, and a preliminary analysis in order to evaluate the homophily of each context.

A Logical Key Hierarchy Based Approach to Preserve Content Privacy in Decentralized Online Social Networks

Distributed Online Social Networks (DOSNs) have been proposed to shift the control over user data from a unique entity, the online social network provider, to the users of the DOSN themselves. In this paper we focus on the problem of preserving the privacy of the contents shared to large groups of users. In general, content privacy is enforced by encrypting the content, having only authorized parties being able to decrypt it. When efficiency has to be taken into account, new solutions have to be devised that: i) minimize the re-encryption of the contents published in a group when the composition of the group changes; and, ii) enable a fast distribution of the cryptographic keys to all the members ( $n$ n ) of a group, each time a set of users is removed from or added to the group by the group owner. Current solutions fall short in meeting the above criteria, while our approach requires only $O(d\cdot log_d (n))$ O ( d · l o g d ( n ) ) encryption operations when a user is removed from a group (where $d$ d is an input parameter of the system), and $O(2\cdot log_d (n))$ O ( 2 · l o g d ( n ) ) when a user joins the group. The effectiveness of our approach is evaluated through simulations based on a real online social network.

Social Overlays Meet the Cloud: A Hybrid Architecture for Profile Dissemination in Decentralized Social Networks

Decentralized online social networks (OSNs) have attracted the attention of researchers and practitioners as a viable alternative to the current centralized OSNs, whose business model is based on the exploitation of the private data of their users. Yet, pure decentralized models may either require significant investment on the user side in terms of hardware and bandwidth, or may fail to provide the desired user experience. In this paper, we propose a middle-ground solution that mainly relies on a serverless social overlay in which links represent friendship relations, but occasionally complements it with inexpensive storage rented from the cloud. The experimental evaluation based on a real OSN dataset confirms that our solution provides the desired quality of service at a low cost.

Managing social contents in Decentralized Online Social Networks: A survey

The widespread diffusion of Online Social Networks has given unforeseen opportunities for their users to share contents and mutually interact. However, current platforms offer inadequate guarantees as far as concerns the privacy of their users. To address these issues and leave to the users more control on their data, several recent proposals suggest to decentralize the storage of social data, aiming at leaving their control entirely to their owners. This approach has lead to the definition of Decentralized Online Social Networks (DOSNs), ranging from completely decentralized solutions, i.e. P2P solutions, to hybrid systems integrating external and private resources for storing user data. While DOSNs allow users to have more control over their data, they raise new challenges concerning the management and availability of social data. Guaranteeing data availability in a highly dynamic environment, defining proper algorithms for information diffusion and guaranteeing data privacy in a distributed setting are currently open problems in this area.This survey presents an overview of these challenges and of the main solutions presented in the literature. Existing proposals are classified taking into account the strategies adopted to manage social data, focusing on the data availability and on information diffusion. The survey also presents the new privacy issues arising in DOSNs. Finally, an overview of the main open issues in this research area is presented.

Towards the Dynamic Community Discovery in Decentralized Online Social Networks

The community structure is one of the most studied features of the Online Social Networks (OSNs). Community detection guarantees several advantages for both centralized and decentralized social networks. Decentralized Online Social Networks (DOSNs) have been proposed to provide more control over private data. Several challenges in DOSNs can be faced by exploiting communities. The detection of communities and the management of their evolution represents a hard process, especially in highly dynamic environments, where churn is a real problem. In this paper, we focus our attention on the analysis of dynamic community detection in DOSNs by studying a real Facebook dataset. We evaluate two different dynamic community discovery classes to understand which of them can be applied to a distributed environment. Results prove that the social graph has high instability and distributed solutions to manage the dynamism are needed and show that a Temporal Trade-off class is the most promising one.

Enhanced Audit Strategies for Collaborative and Accountable Data Sharing in Social Networks

Data sharing and access control management is one of the issues still hindering the development of decentralized online social networks (DOSNs), which are now gaining more research attention with the recent developments in P2P computing, such as the secure public ledger–based protocols (Blockchains) for monetary systems. In a previous work, we proposed an initial audit–based model for access control in DOSNs. In this article, we focus on enhancing the audit strategies and the privacy issues emerging from records kept for audit purposes. We propose enhanced audit and collaboration strategies, for which experimental results, on a real online social network graph with simulated sharing behavior, show an improvement in the detection rate of bad behavior of more than 50% compared to the basic model. We also provide an analysis of the related privacy issues and discuss possible privacy-preserving alternatives.

Predicting the availability of users' devices in decentralized online social networks

SummaryThe understanding of the user temporal behavior is a crucial aspect for all those systems that rely on user resources for daily operations, such as decentralized online social networks (DOSNs). Indeed, DOSNs exploit the devices of their users to take on and share the tasks needed to provide services such as storing the published data. In the last years, the increasing popularity of DOSN services has changed the way of how people interact with each other by enabling users to connect to these services at any time by using their personal devices (such as notebooks or smartphones). As a result, the availability of data in these systems is strongly affected (or reflected) by the temporal behavior of their users in terms of connections to DOSNs. In this paper, we propose the use of linear predictors to address the problem of the availability of user devices and, hence, data in DOSNs. To validate the proposed approaches, we evaluated their performance conducting a set of simulations exploiting a dataset of temporal information concerning the connections to Facebook collected from a set of users.

SPA: A Secure and Private Auction Framework for Decentralized Online Social Networks

The security and privacy threats on e-commerce have attracted intensive attention recently. The explosive growth of online social networks (OSNs) has made them potential new great marketplaces for e-commerce, which, however, raise serious security and privacyconcerns. This is mainly due to the centralized system architecture where the service provider knows all users’ private data and becomes the single point of failure. To this end, we propose a secure and private auction framework, called SPA, for decentralized online social networks (DOSNs). SPA consists of three phases: identity initiation, buyer-seller matching, and private auction. It requires no trust among the participants but can provide security, privacy, authenticity, non-repudiation, and correctness for the auctions. We analyze the computation and communication complexities of the proposed private auction scheme, which are $O(n+K)$ for each node where $n$ is the number of bidders and $K$ is the number of pricing points. In contrast, those of previous auction schemes are $O(nK)$ at best. The storage complexity is significantly lower than before as well. Security and privacy of SPA are also analyzed. Extensive experiments are conducted to validate the efficiency of SPA.

Developing the Cloud-integrated data replication framework in decentralized online social networks

Decentralized Online Social Network (DOSN) services have been proposed to protect data privacy. In DOSN, the data published by a user and their replicas are only stored in the friend circle of the user. Although full replication can improve Data Availability (DA), pure DOSNs may not deliver sustainable DA. This paper proposes a Cloud-assisted data replication and storage scheme, called Cadros, to improve the DA in DOSN. This paper conducts quantitative analysis about the storage capacity of Cadros, and further models and predicts the level of DA that Cadros can achieve. The data in Cadros are partitioned in such a way that the overhead caused by storing the data in the Cloud is minimized while satisfying the desired DA. This paper also proposes the data placement strategies to realize the desired DA and improve other performance. Experiments have been conducted to verify the effectiveness of Cadros.

Analyzing and Boosting the Data Availability in Decentralized Online Social Networks

Maintaining Data Availability (DA) is a big challenge in Decentralized Online Social Networks (DOSN). Nowadays, the limitation of the storage capacity in DOSN becomes a critical factor that jeopardizes the DA. Therefore, it is desired to determine the relation between the storage capacity of DOSN and the level of DA, and develop an approach to mitigating the limitation of storage capacity. This paper addresses these issues. In this paper, a probabilistic DA model over storage capacity is established. A novel method is then proposed to predict the DA on the fly. Further, a Cloud-assisted DOSN (CDOSN) framework is proposed to enhance the storage capacity and the DA in DOSN. This paper conducts the detailed quantitative analysis about the storage capacity and the DA in CDOSN. Extensive simulation experiments have been conducted to evaluate the effectiveness of the DA model, the on-the-fly prediction and the CDOSN framework.

Comparison of P2P Social Network Architectures

In recent years, online social networks have become very popular. Online social networks (OSN) have been useful to find former classmates or to improve our interaction with friends. Thus, a huge amount of information is generated and consumed by millions of people in these types of networks. Currently, most popular online social networks are based on centralized servers, whom are responsible management and storage all the information. Although the benefits of social networks are well known to most of us, these networks still have many challenges such as scalability, privacy or dependence. In this work, we evaluate P2P infrastructures as alternative platform for developing decentralized online social networks. In particular, we simulate and evaluate a specific social network called Tribler on two types of P2P architectures: super-peer and distributed. Our results shown that OSN based on super-peer reaches best download time than OSN based on a distributed P2P architecture.

A survey on decentralized Online Social Networks

Because of growing popularity of Online Social Networks (OSNs) and huge amount of sensitive shared data, preserving privacy is becoming a major issue for OSN users. While most OSNs rely on a centralized architecture, with an omnipotent Service Provider, several decentralized architectures have recently been proposed for decentralized OSNs (DOSNs). In this work, we present a survey of existing proposals. We propose a classification of previous work under two dimensions: (i) types of approaches with respect to resource provisioning devices and (ii) adopted strategies for three main technical issues for DOSN (decentralizing storage of content, access control and interaction/signaling). We point out advantages and limitations of each approach and conclude with a discussion on the impact of DOSNs on users, OSN providers and other stakeholders.

A taxonomy of decentralized online social networks

Despite their tremendous success, centrally controlled cloud-based Online Social Networks (OSNs) have inherent issues related to user privacy and control. These issues have motivated researchers to make a paradigm shift in the OSN architecture by proposing to replace centrally controlled OSNs with Decentralized OSNs (DOSNs) in a peer-to-peer setting. DOSNs give users more autonomy and the chance to participate in social networks without loosing control over their data. The various DOSN proposals have significant differences in their proposed services, architecture and extent of decentralization. In this survey, we study a number of proposals for peer-to-peer DOSNs, distil a set of criteria to compare them, and provide a taxonomy for their comparison.

Privacy Preservation in Decentralized Online Social Networks

The housing of personal data on large online social networks arouses concerns from privacy advocates and leery users. Researchers have proposed decentralized architectures to create online social networks with technically imposed privacy preservation. This survey of several approaches discusses their privacy benefits, architecture, and suitability for mobile devices.