Karl-Peter Fuchs

EncDNS: A Lightweight Privacy-Preserving Name Resolution Service

Users are increasingly switching to third party DNS resolvers (e. g., Google Public DNS and OpenDNS). The resulting monitoring capabilities constitute an emerging threat to online privacy. In this paper we present EncDNS, a novel lightweight privacy-preserving name resolution service as a replacement for conventional third-party resolvers. The EncDNS protocol, which is based on DNSCurve, encapsulates encrypted messages in standards-compliant DNS messages. User privacy is protected by exploiting the fact that a conventional DNS resolver provides sender anonymity against the EncDNS server. Unlike traditional privacy-preserving techniques like mixes or onion routing, which introduce considerable delays due to routing messages over multiple hops, the EncDNS architecture introduces only one additional server in order to achieve a sufficient level of protection against realistic adversaries. EncDNS is open source software. An initial test deployment is available for public use.

REST-Net: A dynamic rule-based IDS for VANETs

In this paper we introduce REST-Net, a novel Intrusion Detection System for Vehicular Ad Hoc Networks (VANETs) that helps to mitigate the integrity and authenticity challenges introduced by VANETs. At its core, REST-Net uses a dynamic detection engine that monitors and analyzes data sent in VANETs through plausibility checks to detect attacks in form of fake Messages. Unlike previous solutions REST-Net offers high detection rates, adaptive warning levels to prevent interruptions of drivers and a concept for the revocation of fake Messages once an attacker is detected. We present the design and components of REST-Net, discuss its security properties and provide results from an initial feasibility study with a micro-traffic simulator.

VANETsim: An open source simulator for security and privacy concepts in VANETs

Aside from massive advantages in safety and convenience on the road, Vehicular Ad Hoc Networks (VANETs) introduce security risks to the users. Proposals of new security concepts to counter these risks are challenging to verify because of missing real world implementations of VANETs. To fill this gap, we introduce VANETsim, an event-driven simulation platform, specifically designed to investigate application-level privacy and security implications in vehicular communications. VANETsim focuses on realistic vehicular movement on real road networks and communication between the moving nodes. A powerful graphical user interface and an experimentation environment supports the user when setting up or carrying out experiments.

Introducing the gMix Open Source Framework for Mix Implementations

In this paper we introduce the open source software framework gMix which aims to simplify the implementation and evaluation of mix-based systems. gMix is targeted at researchers who want to evaluate new ideas and developers interested in building practical mix systems. The framework consists of a generic architecture structured in logical layers with a clear separation of concerns. Implementations of mix variants and supportive components are organized as plug-ins that can easily be exchanged and extended. We provide reference implementations for several well-known mix concepts.

Grenzen des „digitalen Radiergummis“

ZusammenfassungDer Beitrag zeigt die prinzipiellen und technischen Untauglichkeiten der Durchsetzung des Konzepts eines „digitalen Radiergummis“ auf, mit dem Inhalte im Internet mit einem Verfallsdatum versehen und somit zeitlich begrenzt zugänglich gemacht werden sollen.

A safety-preserving mix zone for VANETs

In vehicular ad hoc networks, vehicles may be tracked due to the frequent sending of beacons containing telemetic data. Even changing the vehicles pseudonym cannot prevent attackers from linking beacons. Previously published solutions require vehicles to stop sending beacons when changing their pseudonyms, resulting in the loss of safety. We propose a novel concept based on the approach of mix zones, providing a compromise between privacy and safety. Therefore we introduce a communication proxy inside the mix zones. Simulations show that this approach is technically feasible, even with common hardware.

Workload modelling for mix-based anonymity services

Evaluating and improving the performance of mix-based anonymity systems in a real-world setting is critical to foster their adoption. However, current research in this field mostly employs unrealistic models for evaluation purposes. Moreover, previously documented results are often difficult to reproduce. We propose two complementary models tailored to the evaluation of mix-based anonymity services. The models enable realistic experiments and are easy to use as they allow to automatically extract workloads from trace files recorded in real networks and replay them in simulations. We also describe our ready-to-use open source evaluation suite that implements the models. Given the suite, researchers can easily create and re-use well-defined workload sets for evaluation purposes. The workloads can be replayed both in discrete-event simulations and distributed experiments. With this initiative we want to foster open research in our discipline.

Generating Realistic Application Workloads for Mix-Based Systems for Controllable, Repeatable and Usable Experimentation

Evaluating and improving the performance of anonymity systems in a real-world setting is critical to foster their adoption. However, current research in this field mostly employs unrealistic models for evaluation purposes. Moreover, previously documented results are often difficult to reproduce. We propose two complementary workload models that operate on network traces in order to improve the evaluation of anonymity systems. In comparison to other approaches our workload models are more realistic, as they derive characteristics from trace files recorded in real networks and preserve dependencies of the flows of individual hosts. We also describe our ready-to-use open source evaluation suite that implements our models. Given our tools, researchers can easily create and re-use well-defined workload sets for evaluation purposes. Finally, we demonstrate the importance of realistic workload models by evaluating a well-known dummy traffic scheme with our tools.

Laribus: Privacy-Preserving Detection of Fake SSL Certificates with a Social P2P Notary Network

In this paper we present Laribus, a peer-to-peer network designed to detect local man-in-the-middle attacks against SSL/TLS. With Laribus clients can validate the authenticity of a certificate presented to them by retrieving it from different vantage points on the network. Unlike previous solutions, clients do not have to trust a central notary service, nor do they have to rely on the cooperation of website owners. The Laribus network is based on a Social Network graph, which allows users to form Notary Groups that improve both privacy and availability. It integrates several well-known techniques, such as secret sharing, ring signatures, layered encryption, range queries and a Distributed Hash Table (DHT), to achieve privacy-aware queries, scalability and decentralization. We present the design and core components of Laribus, discuss its security properties and also provide results from a simulation-based feasibility study.