Thorsten Strufe

Technische Universität Dresden, Dresden, Saxony, Germany

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Publications (105)17.88 Total impact

  • Hani Salah · Thorsten Strufe
    No preview · Conference Paper · Jun 2016
  • Source
    Stefanie Roos · Martin Beck · Thorsten Strufe
    [Show abstract] [Hide abstract] ABSTRACT: Friend-to-friend (F2F) overlays, which restrict direct communication to mutually trusted parties, are a promising substrate for privacy-preserving communication due to their inherent membership-concealment and Sybil-resistance. Yet, existing F2F overlays suffer from a low performance, are vulnerable to denial-of-service attacks, or fail to provide anonymity. In particular , greedy embeddings allow highly efficient communication in arbitrary connectivity-restricted overlays but require communicating parties to reveal their identity. In this paper, we present a privacy-preserving routing scheme for greedy embeddings based on anonymous return addresses rather than identifying node coordinates. We show that the return addresses allow plausible deniability. Furthermore, we enhance the routing's resilience by using multiple embeddings and propose a method for efficient content addressing. Our extensive simulation study on real-world data indicates that our approach is highly efficient and effectively mitigates failures as well as powerful denial-of-service attacks.
    Full-text · Conference Paper · Apr 2016
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    Stefanie Roos · Thorsten Strufe · Tu Dresden
    Full-text · Article · Jan 2016
  • Stefanie Roos · Martin Beck · Thorsten Strufe
    [Show abstract] [Hide abstract] ABSTRACT: Friend-to-friend (F2F) overlays, which restrict direct communication to mutually trusted parties, are a promising substrate for privacy-preserving communication due to their inherent membership-concealment and Sybil-resistance. Yet, existing F2F overlays suffer from a low performance, are vulnerable to denial-of-service attacks, or fail to provide anonymity. In particular, greedy embeddings allow highly efficient communication in arbitrary connectivity-restricted overlays but require communicating parties to reveal their identity. In this paper, we present a privacy-preserving routing scheme for greedy embeddings based on anonymous return addresses rather than identifying node coordinates. We prove that the presented algorithm are highly scalalbe, with regard to the complexity of both the routing and the stabilization protocols. Furthermore, we show that the return addresses provide plausible deniability for both sender and receiver. We further enhance the routing's resilience by using multiple embeddings and propose a method for efficient content addressing. Our simulation study on real-world data indicates that our approach is highly efficient and effectively mitigates failures as well as powerful denial-of-service attacks.
    No preview · Article · Jan 2016
  • No preview · Article · Jan 2016 · Computer Communications
  • Hani Salah · Stefanie Roos · Thorsten Strufe
    [Show abstract] [Hide abstract] ABSTRACT: The family of Kademlia-type systems represents the most efficient and most widely deployed class of internet-scale distributed systems. Its success has caused plenty of large scale measurements and simulation studies, and several improvements have been introduced. Kademlia’s use of parallel and non- deterministic lookups, however, so far has prevented any concise formal analysis. We introduce a comprehensive formal model of the routing of the entire family of systems that is validated against both simulations and real-world measurements. In particular, we extend our previous work by excluding the effect of churn into the model. Our evaluation additionally shows that several of the recent improvements to the protocol in fact are counter-productive and identifies preferable designs with regard to routing overhead and robustness to failures.
    No preview · Chapter · Jan 2016
  • Hani Salah · Julian Wulfheide · Thorsten Strufe
    [Show abstract] [Hide abstract] ABSTRACT: Named-Data Networking (NDN) is a promising architecture for future Internet. Its design, however, can be misused to perform a new DDoS attack known as the Interest Flooding Attack (IFA). In IFA, the attacker issues non-satisfiable interest packets, aiming to drop legitimate interest packets by overwhelming pending interest tables in NDN routers. Prior defence mechanisms can be not highly effective, harm legitimate interest packets, and/or incur high overhead. We propose a coordinated defence mechanism against IFAs. We realize our solution by adapting CoMon, a framework that we developed previously to coordinate caching-related decisions in NDN, motivated by its effective, yet affordable, coordination. In our solution, IFAs are detected and mitigated by few routers based on aggregated knowledge of traffic and forwarding states. These routers are selected by a novel heuristic enabling them to observe majority of traffic at early stage. Extensive simulations confirm the feasibility and effectiveness of the solution.
    No preview · Conference Paper · Oct 2015
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    Hani Salah · Stefanie Roos · Thorsten STrufe
    [Show abstract] [Hide abstract] ABSTRACT: The family of Kademlia-type systems represents the most efficient and most widely deployed class of internet scale distributed systems. However, prior research on these systems has mainly been restricted to analyzing deployed systems and suggesting improvements tailored to specific environments rather than exploiting the huge parameter space governing the routing performance. Concise analytic results are rare, due to the complexity of Kademlia’s parallel and non-deterministic lookups. This paper introduces the first comprehensive formal model of the routing for the entire family of Kademlia-type systems. We validate our model against simulations of both the BitTorrent Mainline DHT and eMule’s KAD implementation. The model allows a highly scalable comparison with respect to the hop distribution of different variations to the original protocol. In particular, we show that several of the recent improvements to the protocol in fact have been counterproductive with regard to routing efficiency.
    Full-text · Conference Paper · Aug 2015
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    Stefanie Roos · Thorsten Strufe
    [Show abstract] [Hide abstract] ABSTRACT: Virtual overlays generate topologies for greedy routing , like rings or hypercubes, on connectivity restricted networks. They have been proposed to achieve efficient content discovery in the Darknet mode of Freenet, for instance, which provides a private and secure communication platform for dissidents and whistle-blowers. Virtual overlays create tunnels between nodes with neighboring addresses in the topology. The routing performance hence is directly related to the length of the tunnels, which have to be set up and maintained at the cost of communication overhead in the absence of an underlying routing protocol. In this paper, we show the impossibility to efficiently maintain sufficiently short tunnels. Specifically, we prove that in a dynamic network either the maintenance or the routing eventually exceeds polylog cost in the number of participants. Our simulations additionally show that the length of the tunnels increases fast if standard maintenance protocols are applied. Thus, we show that virtual overlays can only offer efficient routing at the price of high maintenance costs.
    Full-text · Conference Paper · May 2015
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    Thomas Paul · Daniel Puscher · Thorsten Strufe
    [Show abstract] [Hide abstract] ABSTRACT: Privacy in Online Social Networks (OSNs) evolved from a niche topic to a broadly discussed issue in a wide variety of media. Nevertheless, OSNs drastically increase the amount of information that can be found about individuals on the web. To estimate the dimension of data leakage in OSNs, we measure the real exposure of user content of 4,182 Facebook users from 102 countries in the most popular OSN, Facebook. We further quantify the impact of a comprehensible privacy control interface that has been shown to extremely decrease configuration efforts as well as misconfiguration in audience selection. Our study highlights the importance of usable security. (i) The total amount of content that is visible to Facebook users does not dramatically decrease by simplifying the audience selection interface, but the composition of the visible content changes. (ii) Which information is uploaded to Facebook as well as which information is shared with whom strongly depends on the user's country of origin.
    Full-text · Article · May 2015
  • Thomas Paul · Daniel Puscher · Thorsten Strufe
    [Show abstract] [Hide abstract] ABSTRACT: Online Social Networking is a fascinating phenomena, attracting more than one billion people. It supports basic human needs such as communication, socializing with others and reputation building. Thus, an in-depth understanding of user behavior in Online Social Networks (OSNs) can provide major insights into human behavior, and impacts design choices of social platforms and applications. However, researchers have only limited access to behavioral data. As a consequence of this limitation, user behavior in OSNs as well as its development in recent years are still not deeply understood. In this paper, we present a study about user behavior on the most popular OSN, Facebook, with 2071 participants from 46 countries. We elaborate how Facebookers orchestrate the offered functions to achieve individual benefit in 2014 and evaluate user activity changes from 2009 till 2014 to understand the development of user behavior. Inter alia, we focus on the most important functionality, the newsfeed, to understand content sharing amongst users. We (i) yield a better understanding on content sharing and consumption and (ii) refine behavioral assumptions in the literature to improve the performance of alternative social platforms. Furthermore, we (iii) contribute evidence to the discussion of Facebook to be an aging network.
    No preview · Article · May 2015
  • Hani Salah · Julian Wulfheife · Thorsten Strufe
    [Show abstract] [Hide abstract] ABSTRACT: Named-Data Networking (NDN) is a promising architecture for future Internet. However, routers and content providers in NDN can be targets for a new DDoS attack called the Interest Flooding Attack (IFA). As a consequence, affected routers drop legitimate interest packets. We argue that IFA can be defended effectively when it is detected and mitigated, at early stage, based on timely and aggregated information of exchanged packets and forwarding states. Towards this end, we adapt CoMon, a framework that we developed formerly to coordinate caching-related decisions in NDN. This choice is motivated by CoMon’s proven ability to realize efficient, yet lightweight, coordination. A preliminary evaluation confirms the effectiveness of our solution against IFAs.
    No preview · Conference Paper · Apr 2015
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    Stefanie Roos · Giang T Nguyen · Thorsten Strufe
    [Show abstract] [Hide abstract] ABSTRACT: Mathematical modeling and analysis of distributed systems, mostly applied with the goal of the correctness or asymptotic behavior of a system, rarely provides concrete results and often disregards or simplifies network dynamics. However, concrete performance bounds on a system under churn are highly useful both as a validation of empirical results and a scalable alternative to simulations. In this paper, we first present an abstract methodology for deriving the success probability of an action, such as routing, in a dynamic system, using the session length distribution as the decisive parameter. We evaluate the developed methodology by giving concrete bounds on the success probability of recursive routing. The results do not only show the adaptability of our model, but also reveal that a considerable fraction of routing attempts fails due to a leaving node on the return path rather than due to not reaching the target.
    Full-text · Conference Paper · Mar 2015
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    [Show abstract] [Hide abstract] ABSTRACT: Conducting data analysis and system monitoring in a privacy-preserving manner is extremely important for anonymity systems such as the distributed publication system Freenet. The current obfuscation mechanisms for gathering statistics in Freenet are designed to anonymize both the responding node and the response itself. We show that due to the possibility of repeated targeted queries, hidden information, which can be potentially abused to damage both individual users and the system as a whole, about specific nodes can be derived using Bayesian Statistics. Our evaluation, using both an in-depth simulation study and real-world measurements, show that the hidden information can be inferred accurately in more than 86% of all experiments, with a relative error below 0.05 in more than 99.5% of all considered scenarios. Furthermore, we present an initial design for an improved obfuscation method, which is guaranteed to provide k-anonymity.
    Full-text · Conference Paper · Mar 2015
  • Hani Salah · Thorsten Strufe
    [Show abstract] [Hide abstract] ABSTRACT: The autonomous cache management in Content-Centric Networking (CCN) results in suboptimal caching decisions and implies cache-ignorant routing. Cache coordination and similar improvements hence have been the subject of several recent studies. The proposed solutions, however, are either impractical due to their massive coordination overhead, or of limited benefit since they cannot realize perfect coordination. We present CoMon, an architecture for network-wide coordinated caching. CoMon realizes an affordable, yet highly effective, coordination by assigning monitoring and cache-aware (re)routing tasks to only a few nodes, through which the majority of traffic is expected or enforced to pass. CoMon, by design, can maximize the diversity of cached contents and minimize cache replacements. In addition, our simulation study using ISP topologies, shows that CoMon under a pressuring scenario, when coordinates as few as 5% of the nodes, reduces the server hit ratio of both CCN and notable related work by up to 45%. Index Terms: Information-Centric Networking; Coordinated Caching; Cache-Aware Routing
    No preview · Conference Paper · Jan 2015
  • Thomas Paul · Daniel Puscher · Stefan Wilk · Thorsten Strufe
    [Show abstract] [Hide abstract] ABSTRACT: Huge quantities of videos are shared via Online Social Networks (OSN) like Facebook and are watched on mobile devices. Internet connections via cellular networks (UMTS / LTE) require the scarce resources radio bandwidth and battery power. Prefetching of videos in areas of WLAN availability has the potential to reduce the power consumption in comparison to data transmission via cellular networks and prefetching can help to avoid users running into traffic caps of their network providers. Furthermore, startup delays can be reduced. Social networks offer contextual information such as likes and comments as well as social graph information which can potentially be used to predict which content will be consumed in the near future. In this paper, we elaborate possibilities to predict content consumption based on the number of likes, comments and the social graph distance. Our detailed analysis of the media access patterns of more than 700 users in Facebook shows that the media consumption does not solely depend on the number of likes or comments. Users tend to watch videos that are uploaded by close friends and family members. Furthermore, the time a video preview stays in the browser-viewport before being clicked (pre-click delay) can be exploited to decrease startup delays.
    No preview · Conference Paper · Jan 2015
  • Irina Heimbach · Benjamin Schiller · Thorsten Strufe · Oliver Hinz
    No preview · Conference Paper · Jan 2015
  • Paul Gebelein · Thomas Paul · Thorsten Strufe · Wolfgang Effelsberg
    No preview · Article · Jan 2015 · PIK - Praxis der Informationsverarbeitung und Kommunikation
  • Daniel Germanus · Stefanie Roos · Thorsten Strufe · Neeraj Suri
    [Show abstract] [Hide abstract] ABSTRACT: Peer-to-Peer (P2P) protocols usage is proliferating for a variety of applications including time-and safety-critical ones. While the distributed design of P2P provides inherent fault tolerance to certain failures, the large-scale decentralized coordination exhibits various exploitable security threats. One of these key threats are Eclipse attacks, where a large fraction of malicious peers can surround, i.e., eclipse benign peers. Topology-aware localized Eclipse attacks (taLEAs) are a new class of such attacks that allows for highly efficient denial of service attacks with a small amount of malicious resources. Our contribution is twofold: First, we show the generic susceptibility of structured P2P protocols to taLEAs. Second, we propose a new lookup mechanism for the proactive and reactive detection and mitigation of such attacks. Our novel lookup mechanism complements the common deterministic lookup with randomized decisions in order to reduce the predictability of the lookup. We validate our proposed technique via extensive simulations, increasing the lookup success to 100% in many scenarios.
    No preview · Article · Dec 2014
  • Thomas Paul · Marius Hornung · Thorsten Strufe
    No preview · Conference Paper · Dec 2014

Publication Stats

903 Citations
17.88 Total Impact Points

Institutions

  • 2015-2016
    • Technische Universität Dresden
      Dresden, Saxony, Germany
  • 2010-2013
    • Technical University Darmstadt
      • Telecooperation Lab (TK)
      Darmstadt, Hesse, Germany
  • 2011
    • Universität Mannheim
      Mannheim, Baden-Württemberg, Germany
  • 2008-2009
    • University of Nice-Sophia Antipolis
      Nice, Provence-Alpes-Côte d'Azur, France
  • 2003
    • Technische Universität Ilmenau
      Stadt Ilmenau, Thuringia, Germany