We will review some of the major results in random graphs and some of the more challenging open problems. We will cover algorithmic and structural questions. We will touch on newer models, including those related to the WWW.

Random graphs

Intermittently connected mobile networks are sparse wireless networks where most of the time there does not exist a complete path from the source to the destination. These networks fall into the general category of Delay Tolerant Networks. There are many real networks that follow this paradigm, for example, wildlife tracking sensor networks, military networks, inter-planetary networks, etc. In this context, conventional routing schemes would fail.To deal with such networks researchers have suggested to use flooding-based routing schemes. While flooding-based schemes have a high probability of delivery, they waste a lot of energy and suffer from severe contention, which can significantly degrade their performance. Furthermore, proposed efforts to significantly reduce the overhead of flooding-based schemes have often be plagued by large delays. With this in mind, we introduce a new routing scheme, called Spray and Wait, that "sprays" a number of copies into the network, and then "waits" till one of these nodes meets the destination.Using theory and simulations we show that Spray and Wait outperforms all existing schemes with respect to both average message delivery delay and number of transmissions per message delivered; its overall performance is close to the optimal scheme. Furthermore, it is highly scalable retaining good performance under a large range of scenarios, unlike other schemes. Finally, it is simple to implement and to optimize in order to achieve given performance goals in practice.

/pdf/spray-and-wait-an-efficient-routing-scheme-for-50seq3wqos.pdf

Spray and wait: an efficient routing scheme for intermittently connected mobile networks

Wireless vehicular communication has the potential to enable a host of new applications, the most important of which are a class of safety applications that can prevent collisions and save thousands of lives. The automotive industry is working to develop the dedicated short-range communication (DSRC) technology, for use in vehicle-to-vehicle and vehicle-to-roadside communication. The effectiveness of this technology is highly dependent on cooperative standards for interoperability. This paper explains the content and status of the DSRC standards being developed for deployment in the United States. Included in the discussion are the IEEE 802.11p amendment for wireless access in vehicular environments (WAVE), the IEEE 1609.2, 1609.3, and 1609.4 standards for Security, Network Services and Multi-Channel Operation, the SAE J2735 Message Set Dictionary, and the emerging SAE J2945.1 Communication Minimum Performance Requirements standard. The paper shows how these standards fit together to provide a comprehensive solution for DSRC. Most of the key standards are either recently published or expected to be completed in the coming year. A reader will gain a thorough understanding of DSRC technology for vehicular communication, including insights into why specific technical solutions are being adopted, and key challenges remaining for successful DSRC deployment. The U.S. Department of Transportation is planning to decide in 2013 whether to require DSRC equipment in new vehicles.

Dedicated Short-Range Communications (DSRC) Standards in the United States

In this paper, we define and explore proofs of retrievability (PORs). A POR scheme enables an archive or back-up service (prover) to produce a concise proof that a user (verifier) can retrieve a target file F, that is, that the archive retains and reliably transmits file data sufficient for the user to recover F in its entirety.A POR may be viewed as a kind of cryptographic proof of knowledge (POK), but one specially designed to handle a large file (or bitstring) F. We explore POR protocols here in which the communication costs, number of memory accesses for the prover, and storage requirements of the user (verifier) are small parameters essentially independent of the length of F. In addition to proposing new, practical POR constructions, we explore implementation considerations and optimizations that bear on previously explored, related schemes.In a POR, unlike a POK, neither the prover nor the verifier need actually have knowledge of F. PORs give rise to a new and unusual security definition whose formulation is another contribution of our work.We view PORs as an important tool for semi-trusted online archives. Existing cryptographic techniques help users ensure the privacy and integrity of files they retrieve. It is also natural, however, for users to want to verify that archives do not delete or modify files prior to retrieval. The goal of a POR is to accomplish these checks without users having to download the files themselves. A POR can also provide quality-of-service guarantees, i.e., show that a file is retrievable within a certain time bound.

PORs: Proofs of Retrievability for Large Files

Vehicular networks are very likely to be deployed in the coming years and thus become the most relevant form of mobile ad hoc networks. In this paper, we address the security of these networks. We provide a detailed threat analysis and devise an appropriate security architecture. We also describe some major design decisions still to be made, which in some cases have more than mere technical implications. We provide a set of security protocols, we show that they protect privacy and we analyze their robustness and efficiency.

/pdf/securing-vehicular-ad-hoc-networks-4sgegi8hgk.pdf

Securing vehicular ad hoc networks

MobiCom Poster: Toward a Mobility Metric for Comparable & Reproducible Results in Ad Hoc Networks Research

Payment channel networks are a highly discussed approach for improving scalability of cryptocurrencies such as Bitcoin. As they allow processing transactions off-chain, payment channel networks are referred to as second layer technology, while the blockchain is the first layer. We uncouple payment channel networks from blockchains and look at them as first-class citizens. This brings up the question what model payment channel networks require as first layer. In response, we formalize a model (called RFL Model) for a first layer below a payment channel network. While transactions are globally made available by a blockchain, the RFL Model only provides the reduced property that a transaction is delivered to the users being affected by a transaction. We show that the reduced model's properties still suffice to implement payment channels. By showing that the RFL Model can not only be instantiated by the Bitcoin blockchain but also by trusted third parties like banks, we show that the reduction widens the design space for the first layer. Further, we show that the stronger property provided by blockchains allows for optimizations that can be used to reduce the time for locking collateral during payments over multiple hops in a payment channel network.

Fundamental Properties of the Layer Below a Payment Channel Network (Extended Version).

Today, many Internet users take part in online social networks (OSNs) like Facebook, Xing, LinkedIn, MySpace, studiVZ, and others. However, the motives for participation are multifaceted and stand in contrast to the motivation not to join OSNs because of the potential danger with respect to privacy aspects. This risk is already perceived by some OSN users but still underestimated. The naive handling with personal data inside such networks combined with many possibilities to link several OSN profiles of a single user paves the way for third-parties to gather the comprehensive virtual appearance of a person. Therefore, to turn the tables, such correlations of information might be useful to demonstrate to a user a measure of how linkable his personal data is, given the current exposure of his public data in OSN profiles. In this paper we point out some astonishing simple ways to automatically link data from different OSNs. As we want to and have to act compliant to the German data protection laws, we analyze corresponding requirements and sketch our concept for compliant statistical sampling. We further show preliminary results regarding successful profile correlations based on, even under legal and technical constraints, extracted friends lists.

https://www.dfn.de/fileadmin/3Beratung/DFN-Forum4/Labitzke-Dinger-Hartenstein.pdf

How I and others can link my various social network profiles as a basis to reveal my virtual appearance

Der Beitrag beschreibt wesentliche seit dem Jahr 2005 an der Universitat Karlsruhe bzw. am Karlsruher Institut fur Technologie erzielte Ergebnisse in Bezug auf technische und organisatorische Integration fur das Informationsmanagement. Insbesondere stehen die Portaldienste und das Identitatsmanagement im Fokus der technischen Innovation. Daneben werden zwei organisatorische Innovationen vorgestellt, die sich dediziert Fragestellungen zur IT-Governance und IT-Compliance widmen. Abschliesend werden erzielte Schlusselerfahrungen diskutiert, die im Zuge des Aufbaus eines integrierten Informationsmanagements gemacht wurden. Ausblickend wollen wir einen Bezug zu den allgegenwartigen Problemstellungen und verbundenen Herausforderungen derartiger Vorhaben aufzeigen – Herausforderungen, die waren, sind und bleiben werden.

Integriertes Informationsmanagement am KIT Was bleibt? Was kommt?

ZUSAMMENFASSUNG Dieser Artikel beschreibt die Architektur eines integrierten Identitätsmanagements an einer Universität. Der beschriebene Ansatz basiert auf der Sicht der Universität als Föderation organisatorischer Einheiten und auf dem Prinzip der Dienstorientierung. Die Datenhaltung von Identitätsinformation erfolgt dezentral, wobei lediglich Abbildungsinformation, die für das “in Beziehung setzen” von Identitätsinformation zwischen den organisatorischen Einheiten notwendig ist, zentral vorgehalten wird, wenn dies vom Nutzer gewünscht wird. Der Aufbau eines solchen Systems und die technische Realisierung, welche klassische Identitätsmanagementkomponenten mit einem modernen, auf Web Services basierenden Ansatz vereint, werden anhand der Umsetzung an der Universität Karlsruhe beschrieben.

Hannes Hartenstein

Papers

MobiCom Poster: Toward a Mobility Metric for Comparable & Reproducible Results in Ad Hoc Networks Research

Fundamental Properties of the Layer Below a Payment Channel Network (Extended Version).

How I and others can link my various social network profiles as a basis to reveal my virtual appearance

Integriertes Informationsmanagement am KIT Was bleibt? Was kommt?

Föderatives und dienstorientiertes Identitätsmanagement: Konzept und Erfahrungen