research - design - experience

Computer Science Research

Jens Oberender works with the computer networks & communications group of Hermann de Meer at the University of Passau.

His reach field comprises IT-security, network privacy, the Peer-to-Peer paradigm and network cooperative.
Jens Oberender's PhD thesis researches resilience of anonymity networks.
In this section you can find recent publications, technical reports and patents.

Grundlagen Kooperativer Anonymisierungsnetze

Um einen hohen Grad an Anonymität zu erhalten, müssen für Teilnehmer mit egoistischem Verhalten Anreize für Kooperation geschaffen werden. Bedeutungslose Nachrichten können die Unbeobachtbarkeit für andere Teilnehmer erhöhen. Mittels eines Anreizmechanismus lässt sich der Versand eigener Nachrichten an das Volumen bedeutungsloser Nachrichten koppeln. Allerdings muss sichergestellt werden, dass gegenüber einem Angreifer bedeutungslose Nachrichten ununterscheidbar sind. Kooperative Mechanismen könnten allerdings die Widerstandsfähigkeit von Anonymisierungsnetzen weiter verbessern.

 

Weiterlesen: Grundlagen Kooperativer Anonymisierungsnetze

SIGCOMM 2005 review

The Special Interest Group on Communications gives one of the most famous computer science conferences, abbreviated SIGCOMM. The conference features landmark research. In this talk, I introduce interesting topics of the 205 SIGCOMM.

Weiterlesen: SIGCOMM 2005 review

What Peer-to-Peer can learn from network attacks

Peer-to-peer overlays have been based on altrusitic and cooperative behavior. This assumption ignores malicous behavior, which aims at increased benefit of an attacker.

Weiterlesen: What Peer-to-Peer can learn from network attacks

Denial-of-Service Flooding Detection in Anonymity Networks

Denial-of-Service (DoS) flooding attackers benefit from sender anonymity and exit node diversity. Anonymity networks provide this by hiding he communication relationship and therefore hinder attack detection. After the anonymity network purges IP headers, the attributes for clustering of traffic flows remain hidden. Message unlinkability provides network privacy.
We design limited message linkability for clustering of traffic flows.Clusters of anonymous traffic are sufficient for flooding attack detection and also enable mitigation. The number of linkable messages is restricted to limit profile size and protect from privacy adversaries. In distributed scenarios, our incentive motivates use of a single entity.
Message tags enable detection of flooding attacks. The set of linkable messages is limited, which cuts activity profile. Adversaries cannot influence message linkability of other parties. Senders dynamically govern their message linkability through the message arrival rate. During flooding to a single victim message linkability improves, enabling DoS detection for anonymity networks.

Weiterlesen: Denial-of-Service Flooding Detection in Anonymity Networks

On the Design Dilemma in Dining Cryptographer Networks

In a Dining Cryptographers network, the anonymity level raises with the number of participating users. This paper studies strategic behavior based on game theory. Strategic user behavior can cause sudden changes to the number of system participants and, in consequence, degrade anonymity. This is caused by system parameters that influence strategic behavior. Additionally, conflicting goals of participants result in dilemma games. Properties of message coding, e.g. collision robustness and disrupter identification, change the game outcome by preventing dilemmas and, therefore, enhance anonymity. Properties of anonymity metrics are proposed that allow for strategic user behavior.

Weiterlesen: On the Design Dilemma in Dining Cryptographer Networks

Simulative Performance Evaluation of a Mobile Peer-to-Peer File-Sharing System

Peer-to-Peer (P2P) file-sharing has become the killer application in the wired Internet and might also be highly attractive for mobile networks. In particular since UMTS operators are searching for new applications which do both: a) exploit the potential of the UMTS technology and b) motivate the user to adopt the new technology. In this work we are investigating the performance of an eDonkey-based mobile P2P filesharing system bymeans of time-dynamic simulation. Mobile networks differ from wireline networks by the limited capacity of the radio link and the mobility of the users. P2P networks, in contrast, are overlays which consider the transport network in an abstract way. In a mobile environment, the question arises, whether the abstraction can be maintained and what will be the performance impact if there is any. We will show in detail how the mobile access technology (GPRS or UMTS), the churn behavior of mobile users, the file size of mobile specific content, and special infrastructure entities, such as a cache peer, influences the performance of the suggested mobile P2P file-sharing service.

Weiterlesen: Simulative Performance Evaluation of a Mobile Peer-to-Peer File-Sharing System

P2P Replication Revisited: Mobile Infrastructures

Traffic engineering in P2P networks deals with organizing overlay networks. The challenge of unavailability has not been mastered yet. Considering the resource allocation can gain further improvements. While adapting P2P file sharing into mobile infrastructures, we learned that replication is a solution to both issues: availability and traffic optimization.

Weiterlesen: P2P Replication Revisited: Mobile Infrastructures

An Architecture Concept for Mobile P2P File Sharing Services

File-sharing in mobile networks has differing demands to a P2P architecture. Resource access and mediation techniques must follow constraints given in 2.5G/3G networks. Enhancing the eDonkey protocol, we reconcile decentralized operation with traffic control.

Weiterlesen: An Architecture Concept for Mobile P2P File Sharing Services

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