Low-resource eclipse attacks on Ethereum’s peer-to-peer network

We present eclipse attacks on Ethereum nodes that exploit the peer-to-peer network used for neighbor discovery. Our attacks can be launched using only two hosts, each with a single IP address. Our eclipse attacker monopolizes all of the victim’s incoming and outgoing connections, thus isolating the victim from the rest of its peers in the network. The attacker can then filter the victim’s view of the blockchain, or co-opt the victim’s computing power as part of more sophisticated attacks. We argue that these eclipse-attack vulnerabilities result from Ethereum’s adoption of the Kademlia peer-to-peer protocol, and present countermeasures that both harden the network against eclipse attacks and cause it to behave differently from the traditional Kademlia protocol. Several of our countermeasures have been incorporated in the Ethereum geth 1.8 client released on February 14, 2018.First author draf

Eclipsing Ethereum Peers with False Friends

Ethereum is a decentralized Blockchain system that supports the execution of Turing-complete smart contracts. Although the security of the Ethereum ecosystem has been studied in the past, the network layer has been mostly neglected. We show that Go Ethereum (Geth), the most widely used Ethereum implementation, is vulnerable to eclipse attacks, effectively circumventing recently introduced (Geth v1.8.0) security enhancements. We responsibly disclosed the vulnerability to core Ethereum developers; the corresponding countermeasures to our attack where incorporated into the v1.9.0 release of Geth. Our false friends attack exploits the Kademlia-inspired peer discovery logic used by Geth and enables a low-resource eclipsing of long-running, remote victim nodes. An adversary only needs two hosts in distinct /24 subnets to launch the eclipse, which can then be leveraged to filter the victim's view of the Blockchain. We discuss fundamental properties of Geth's node discovery logic that enable the false friends attack, as well as proposed and implemented countermeasures.Comment: Extended version of the original publication in: 2019 IEEE European Symposium on Security and Privacy Workshops (EuroS&PW

Empirical and Analytical Perspectives on the Robustness of Blockchain-related Peer-to-Peer Networks

Die Erfindung von Bitcoin hat ein großes Interesse an dezentralen Systemen geweckt. Eine häufige Zuschreibung an dezentrale Systeme ist dabei, dass eine Dezentralisierung automatisch zu einer höheren Sicherheit und Widerstandsfähigkeit gegenüber Angriffen führt. Diese Dissertation widmet sich dieser Zuschreibung, indem untersucht wird, ob dezentralisierte Anwendungen tatsächlich so robust sind. Dafür werden exemplarisch drei Systeme untersucht, die häufig als Komponenten in komplexen Blockchain-Anwendungen benutzt werden: Ethereum als Infrastruktur, IPFS zur verteilten Datenspeicherung und schließlich "Stablecoins" als Tokens mit Wertstabilität. Die Sicherheit und Robustheit dieser einzelnen Komponenten bestimmt maßgeblich die Sicherheit des Gesamtsystems in dem sie verwendet werden; darüber hinaus erlaubt der Fokus auf Komponenten Schlussfolgerungen über individuelle Anwendungen hinaus. Für die entsprechende Analyse bedient sich diese Arbeit einer empirisch motivierten, meist Netzwerklayer-basierten Perspektive -- angereichert mit einer ökonomischen im Kontext von Wertstabilen Tokens. Dieses empirische Verständnis ermöglicht es Aussagen über die inhärenten Eigenschaften der studierten Systeme zu treffen. Ein zentrales Ergebnis dieser Arbeit ist die Entdeckung und Demonstration einer "Eclipse-Attack" auf das Ethereum Overlay. Mittels eines solchen Angriffs kann ein Angreifer die Verbreitung von Transaktionen und Blöcken behindern und Netzwerkteilnehmer aus dem Overlay ausschließen. Des weiteren wird das IPFS-Netzwerk umfassend analysiert und kartografiert mithilfe (1) systematischer Crawls der DHT sowie (2) des Mitschneidens von Anfragenachrichten für Daten. Erkenntlich wird hierbei, dass die hybride Overlay-Struktur von IPFS Segen und Fluch zugleich ist, da das Gesamtsystem zwar robust gegen Angriffe ist, gleichzeitig aber eine umfassende Überwachung der Netzwerkteilnehmer ermöglicht wird. Im Rahmen der wertstabilen Kryptowährungen wird ein Klassifikations-Framework vorgestellt und auf aktuelle Entwicklungen im Gebiet der "Stablecoins" angewandt. Mit diesem Framework wird somit (1) der aktuelle Zustand der Stablecoin-Landschaft sortiert und (2) ein Mittel zur Verfügung gestellt, um auch zukünftige Designs einzuordnen und zu verstehen.The inception of Bitcoin has sparked a large interest in decentralized systems. In particular, popular narratives imply that decentralization automatically leads to a high security and resilience against attacks, even against powerful adversaries. In this thesis, we investigate whether these ascriptions are appropriate and if decentralized applications are as robust as they are made out to be. To this end, we exemplarily analyze three widely-used systems that function as building blocks for blockchain applications: Ethereum as basic infrastructure, IPFS for distributed storage and lastly "stablecoins" as tokens with a stable value. As reoccurring building blocks for decentralized applications these examples significantly determine the security and resilience of the overall application. Furthermore, focusing on these building blocks allows us to look past individual applications and focus on inherent systemic properties. The analysis is driven by a strong empirical, mostly network-layer based perspective; enriched with an economic point of view in the context of monetary stabilization. The resulting practical understanding allows us to delve into the systems' inherent properties. The fundamental results of this thesis include the demonstration of a network-layer Eclipse attack on the Ethereum overlay which can be leveraged to impede the delivery of transaction and blocks with dire consequences for applications built on top of Ethereum. Furthermore, we extensively map the IPFS network through (1) systematic crawling of its DHT, as well as (2) monitoring content requests. We show that while IPFS' hybrid overlay structure renders it quite robust against attacks, this virtue of the overlay is simultaneously a curse, as it allows for extensive monitoring of participating peers and the data they request. Lastly, we exchange the network-layer perspective for a mostly economic one in the context of monetary stabilization. We present a classification framework to (1) map out the stablecoin landscape and (2) provide means to pigeon-hole future system designs. With our work we not only scrutinize ascriptions attributed to decentral technologies; we also reached out to IPFS and Ethereum developers to discuss results and remedy potential attack vectors

Security Engineering of Patient-Centered Health Care Information Systems in Peer-to-Peer Environments: Systematic Review

Background: Patient-centered health care information systems (PHSs) enable patients to take control and become knowledgeable about their own health, preferably in a secure environment. Current and emerging PHSs use either a centralized database, peer-to-peer (P2P) technology, or distributed ledger technology for PHS deployment. The evolving COVID-19 decentralized Bluetooth-based tracing systems are examples of disease-centric P2P PHSs. Although using P2P technology for the provision of PHSs can be flexible, scalable, resilient to a single point of failure, and inexpensive for patients, the use of health information on P2P networks poses major security issues as users must manage information security largely by themselves. Objective: This study aims to identify the inherent security issues for PHS deployment in P2P networks and how they can be overcome. In addition, this study reviews different P2P architectures and proposes a suitable architecture for P2P PHS deployment. Methods: A systematic literature review was conducted following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) reporting guidelines. Thematic analysis was used for data analysis. We searched the following databases: IEEE Digital Library, PubMed, Science Direct, ACM Digital Library, Scopus, and Semantic Scholar. The search was conducted on articles published between 2008 and 2020. The Common Vulnerability Scoring System was used as a guide for rating security issues. Results: Our findings are consolidated into 8 key security issues associated with PHS implementation and deployment on P2P networks and 7 factors promoting them. Moreover, we propose a suitable architecture for P2P PHSs and guidelines for the provision of PHSs while maintaining information security. Conclusions: Despite the clear advantages of P2P PHSs, the absence of centralized controls and inconsistent views of the network on some P2P systems have profound adverse impacts in terms of security. The security issues identified in this study need to be addressed to increase patients\u27 intention to use PHSs on P2P networks by making them safe to use

How many eyes are spying on your shared folders?

Today peer-to-peer (P2P) file sharing networks help tens of millions of users to share contents on the Internet. However, users' private files in their shared folders might become accessible to everybody inadvertently. In this paper, we investigate this kind of user privacy exposures in Kad, one of the biggest P2P file sharing networks, and try to answer two questions: Q1. Whether and to what extent does this problem exist in current systems? Q2. Are attackers aware of this privacy vulnerability and are they abusing obtained private information? We build a monitoring system called Dragonfly based on the eclipse mechanism to passively monitor sharing and downloading events in Kad. We also use the Honeyfile approach to share forged private information to observe attackers' behaviors. Based on Dragonfly and Honeyfiles, we give affirmative answers to the above two questions. Within two weeks, more than five thousand private files related to ten sensitive keywords were shared by Kad users, and over half of them come from Italy and Spain. Within one month, each honey file was downloaded for about 40 times in average, and its inner password information was exploited for 25 times. These results show that this privacy problem has become a serious threat for P2P users. Finally, we design and implement Numen, a plug-in for eMule, which can effectively protect user private files from being shared without notice. Copyright 2012 ACM.EI

Ethereum’s Peer-to-Peer Network Monitoring and Sybil Attack Prevention

International audiencePublic blockchains, like Ethereum, rely on an underlying peer-to-peer (P2P) network to disseminate transactions and blocks between nodes. With the rise of blockchain applications and cryptocurrencies values, they have become critical infrastructures which still lack comprehensive studies. In this paper, we propose to investigate the reliability of the Ethereum P2P network. We developed our own dependable crawler to collect information about the peers composing the network. Our data analysis regarding the geographical distribution of peers and the churn rate shows good network properties while the network can exhibit a sudden and major increase in size and peers are highly concentrated on a few ASes. In a second time, we investigate suspicious patterns that can denote a Sybil attack. We find that many nodes hold numerous identities in the network and could become a threat. To mitigate future Sybil attacks, we propose an architecture to detect suspicious nodes and revoke them. It is based on a monitoring system, a smart contract to propagate the information and an external revocation tool to help clients remove their connections to suspicious peers. Our experiment on Ethereum's Test network proved that our solution is effective

TrustedKad - Application of Trust Mechanisms to a Kademlia-Based Peer-to-Peer Network

Peer-to-Peer-Netzwerke (P2P) sind verteilte Systeme, die aus gleichberechtigten Knoten („Peers“) bestehen. Im Gegensatz zu klassischen Client-Server-Systemen gibt es in P2P-Netzwerken keine hierarchischen Ebenen oder zentrale Kontrolleinheiten: Alle Peers bieten gleichzeitig Dienste an und nutzen sie. Im vergangenen Jahrzehnt ist eine Vielzahl verschiedener P2P-Anwendungen entwickelt worden – Filesharing-Anwendungen wie BitTorrent und eMule und Kommunikations-Anwendungen wie Skype gehören zu den bekanntesten von ihnen. Forschungsarbeiten haben gezeigt, dass P2P-Netzwerke anfällig für verschiedene Arten von Angriffen sind. Bekannte Angriffe sind z.B. die Sybil- und die Eclipse-Attack. Die üblichen Gegenmaßnahmen gegen die Angriffe sind Replikation und das Verwenden von disjunkten Routing-Pfaden, um die Wahrscheinlichkeit zu reduzieren, während einer Routing- oder Storage-Operation mit bösartigen Knoten zu interagieren. Seit einiger Zeit wird die Anwendung von Vertrauensmechanismen auf P2P-Netzwerke untersucht. Existierende Arbeiten betrachten meist unstrukturierte P2P-Netzwerke – in realen Umgebungen überwiegen jedoch die strukturierten Netzwerke. Insbesondere Implementierungen des Kademlia-Algorithmus‘ sind weit verbreitet, da er von BitTorrent und eMule genutzt wird. Dennoch versucht keiner der vertrauensbasierten Ansätze, die strukturierte Netzwerke behandeln, speziell die Sicherheit von Kademlia zu verbessern. Aufgrund der Verbreitung von Kademlia wird TrustedKad vom Autor entwickelt, um die Sicherheit des Kademlia-Algorithmus‘ zu verbessern. In dieser Arbeit wird TrustedKad eingeführt und die Funktionsweise erläutert. TrustedKad bewertet das Verhalten von Knoten nach Routing- oder Storage-Operationen als entweder positiv oder negativ. Dafür definiert TrustedKad unter Berücksichtigung der Funktionsweise von Kademlia die Regeln, nach denen gut- und bösartiges Verhalten identifiziert wird. Basierend auf diesen Bewertungen werden Vertrauenswerte für Routing und Storage berechnet, um gutartige und bösartige Knoten zu erkennen. Jeder Knoten nutzt Schwellwerte für diese Vertrauenswerte, um zu entscheiden, welche Knoten er als vertrauenswürdig ansieht. Nicht vertrauenswürdige Knoten werden während der eigenen Operationen eines Knotens vermieden. Darüber hinaus nutzt TrustedKad zusätzliche Sicherheitsfunktionen, um die Sicherheit des Systems weiter zu erhöhen. Diese werden im Verlauf dieser Arbeit vorgestellt. Um TrustedKad zu evaluieren, wird es in einer Simulationsumgebung implementiert und analysiert. Die in dieser Arbeit präsentierten Ergebnisse zeigen, dass TrustedKad in der Lage ist, gutartige und bösartige Knoten zu unterscheiden. Es wehrt verschiedene Variationen von bekannten Angriffen ab und verbessert die Sicherheit von Kademlia-basierten Netzwerken deutlich.Peer-to-peer networks (P2P) are distributed systems that consist of equal nodes (“peers”). In contrast to classic client/server systems, there is no hierarchy or central entity: All peers offer services and use them at the same time. In the past decade, a multitude of different P2P applications has been developed – filesharing applications such as BitTorrent and eMule and communication applications such as Skype are among the most popular of them. Research has shown that P2P networks are vulnerable to different kinds of attacks. Known attacks include, e.g., the Sybil attack and the Eclipse attack. Traditional countermeasures against the attacks are replication and the usage of disjoint routing paths to reduce the probability of interacting with malicious nodes during a routing or storage operation. More recently, trust mechanisms have been proposed and analyzed for applicability to P2P networks. The existing related work mostly targets unstructured P2P networks – however, in real-world environments, the structured networks prevail. Especially implementations of the Kademlia algorithm are widely spread, as it is used by BitTorrent and eMule. Nevertheless, none of the trust-based approaches that aim at structured networks specifically attempts to enhance Kademlia’s security. Due to Kademlia’s prevalence, TrustedKad is particularly designed by the author to improve the security of the Kademlia algorithm. In this thesis, TrustedKad is introduced and its functioning is explained. TrustedKad rates the behavior of nodes after routing and storage operations as either positive or negative. To do so, it defines the rules by which inoffensive and malicious behavior is identified in dependence of the functioning of the Kademlia algorithm. Based on the ratings, routing and storage trust values are calculated to identify inoffensive and malicious nodes. Every node uses thresholds for these trust values to decide which nodes it regards as trustworthy. Non-trustworthy nodes are avoided during a node’s own operations. Furthermore, TrustedKad uses additional security features to further increase the security of the system. They are introduced in this thesis. In order to evaluate TrustedKad, it is implemented and analyzed in a simulation environment. The results presented in this thesis show that TrustedKad is able to distinguish inoffensive and malicious nodes. It counters miscellaneous variations of known attacks and improves the security of Kademlia-based networks considerably