Ingmar Baumgart

OverSim: A Flexible Overlay Network Simulation Framework

A fundamental problem in studying peer-to- peer networks is the evaluation of new protocols. This paper presents OverSim, a flexible overlay network simulation framework based on OMNeT++. It was designed to fulfill a number of requirements that have been partially neglected by existing simulation frameworks. OverSim includes several structured and unstructured peer-to-peer protocols like Chord, Kademlia and Gia. These protocol implementations can be used for both simulation as well as real world networks. To facilitate the implementation of additional protocols and to make them more comparable OverSim provides several common functions like a generic lookup mechanism for structured peer-to-peer networks and an RPC interface. Several exchangeable underlay network models allow to simulate complex heterogeneous underlay networks as well as simplified networks for large- scale simulations. We show that with OverSim simulations of overlay networks with up to 100,000 nodes are feasible.

OverSim: A scalable and flexible overlay framework for simulation and real network applications

OverSim facilitates rapid prototyping of new overlay protocols by providing functions common to most overlay protocols. The framework allows to use the same implementations for scalable simulations and in real networks. OverSim benefits from features like an efficient event scheduler and strong GUI support. The large number of implemented overlay protocols and the availability to collect various statistical data make OverSim a powerful tool and reference platform for the peer-to-peer research community. OverSim is welldocumented, actively developed as an open source project on http://www.oversim.org/, has an active mailing list with a strong user base and is open to contributions.

S/Kademlia: A practicable approach towards secure key-based routing

Security is a common problem in completely decentralized peer-to-peer systems. Although several suggestions exist on how to create a secure key-based routing protocol, a practicable approach is still unattended. In this paper we introduce a secure key-based routing protocol based on Kademlia that has a high resilience against common attacks by using parallel lookups over multiple disjoint paths, limiting free nodeld generation with crypto puzzles and introducing a reliable sibling broadcast. The latter is needed to store data in a safe replicated way. We evaluate the security of our proposed extensions to the Kademlia protocol analytically and simulate the effects of multiple disjoint paths on lookup success under the influence of adversarial nodes.

Privacy-Aware Smart Metering: A Survey

The increasing share of renewables creates new challenges for the existing electrical grid. To deal with these challenges, various efforts are being made to transform the existing power grid into a so-called smart grid. Part of this process is the deployment of an advanced metering infrastructure, which provides novel high-frequency two-way communication between consumers and producers. But as useful as the access to high-frequency measurements may be for energy suppliers, this also poses a major threat to the privacy of the customers. In this survey we present approaches to the problem of customer privacy-protection in the smart grid. We show that the privacy problem in smart grids can be further divided into the problems metering for billing and metering for operations. For each of these problems we identify generic approaches to solve them.

P2PNS: A Secure Distributed Name Service for P2PSIP

Decentralized voice over IP networks are a promising alternative to classical server-based SIP networks especially in disaster areas or areas without centralized infrastructure. This paper presents P2PNS, a secure distributed name service for P2P SIP. P2PNS can be used to resolve SIP AoRs to contact URIs without using DNS or centralized SIP servers. The name service provides several security mechanisms to efficiently prevent identity theft and to ensure the uniqueness of SIP AoRs in a completely decentralized and untrusted network. The proposed two-stage name resolution mechanism allows to efficiently handle frequent IP address changes. Because P2PNS provides a generic name service it is not limited to P2PS1P but can also be used e.g. to build a distributed DNS system.

Fast but economical: A simulative comparison of structured peer-to-peer systems

In the past many proposals for structured peer-to-peer protocols have been published. They differ in properties like overlay topology and routing table maintenance. Furthermore, each protocol exhibits various parameters e.g. to adjust the size of the routing table or stabilization intervals, making it difficult to choose an optimal protocol and parameter set for a given scenario (e.g. churn rate, number of nodes). For this purpose, we developed the overlay simulation framework OverSim and implemented six well known structured overlay protocols. In this paper we first compare these protocols among each other. Furthermore, we study several recursive and iterative routing variants and show the effect of routing table redundancy and lookup parallelism on routing latency and bandwidth costs. For each overlay protocol we identify an optimal parameter set for a typical peer-to-peer scenario. Finally, we show how overlay protocols adapt to variations in churn rate and network size. Our results show considerable advantages of the protocols Kademlia and Bamboo, while De Bruijn based protocols reveal a lack of stability under churn.

Pseudonymous Smart Metering without a Trusted Third Party

Privacy concerns in smart metering are one of the most discussed challenges encountered by introducing the smart grid. Several approaches to tackle this problem exist. One of these approaches is the usage of pseudonyms to protect the privacy of customers. Existing solutions to pseudonymous smart metering require a trusted third party to manage the pseudonyms and often neglect the risk of transmitting pseudonymized data through direct connections. This provides the data sink with a mapping from pseudonym to network address which can be used to break pseudonymization. In this paper, we propose a pseudonymous smart metering protocol that does not require a trusted third party. It provides authenticated but anonymous pseudonyms and solves the transmission problem by using a lightweight anonymity network based on a peer-to-peer overlay.

Elderberry: A peer-to-peer, privacy-aware smart metering protocol

The deployment of smart metering provides an immense amount of data for power grid operators and energy providers. By using this data, a more efficient and flexible power grid can be realized. However, this data also raises privacy concerns since it contains very sensitive information about customers. In this paper, we present Elderberry, a peer-to-peer protocol that enables near real-time smart metering while preserving the customers privacy. By forming small groups of cooperating smart meters, their consumption traces are anonymized before being aggregated and sent to the grid operator. Through aggregation, Elderberry realizes efficient monitoring of large numbers of smart meters. It reaches this goal without computationally complex cryptography and adds only little communication overhead.

OverDrive: an overlay-based geocast service for smart traffic applications

For smart traffic scenarios, communication between traffic participants is of high importance. Classical approaches (e.g. for information about congestions) employ a server-based architecture, which raises scalability and privacy concerns. In this paper, we propose OverDrive, a decentralized overlay-based geocast service that is applicable in smart traffic scenarios and not prone to the shortcomings of centralized designs. Information requests for points in geographic space are routed directly via traffic participants until they reach a node in the proximity of that point. In contrast to other approaches, our overlay is specifically tailored towards supporting mobile nodes-vehicles connected via cellular networks-and leverages their speed and direction for optimizing peering decisions and minimizing maintenance overhead. Exhaustive simulations in complex smart traffic scenarios show that OverDrive achieves high delivery ratios even in high mobility environments. At the same time, communication overhead is kept low, making OverDrive suitable for the use with cellular networks.

Towards Secure User-Centric Networking: Service-Oriented and Decentralized Social Networks

Mobile devices like laptops or smart phones are getting more and more powerful, but still these devices are mainly used to access services, which are provided by centralized servers in the Internet. We argue that the full potential of such mobile devices could be unfold if these devices would provide services like instant messaging or file transfer themselves in a peer-to-peer manner. In this paper, we introduce SODESSON, a middleware which enables easy and secure access to services that get provided by devices belonging to the user himself and his friends or colleagues. This novel communication paradigm of user-centric networking leads to more efficient and secure communication, since the indirection introduced by servers is eliminated. Given that we focus on user-centric communication, we are able to exploit the trust relationships and communication pattern of a social graph to reach these goals.