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

Ensuring the integrity of executable binaries is of vital importance to systems that run and depend on them. Additionally, supply-chain attacks and security related bugs demonstrate that binaries, once deployed, may need to be revoked and replaced with updated versions.Recently, blockchain ecosystems have garnered broad attention as middlewares for decentralised solutions to existing problems. Stengele et al. [4] presented a concept how the Ethereum blockchain and peer-to-peer network can be used to ensure the integrity of binaries with timely, accurate, and machine-readable revocations. In this work, we show this concept in practice with a user client implementation in Go and demonstrate how revocations and updates can reliably reach a user client within minutes. We show the client's ability to ensure the integrity of multiple binaries and continuously monitor the Ethereum blockchain for updates and revocations via an unmodified Ethereum client. We also examine the trust relations and trade-offs through our use case. Since the user client fully relies on an Ethereum client as a gateway, the latter's resilience against malicious actors is crucial to consider in a practical deployment.

/pdf/practical-trade-offs-in-integrity-protection-for-binaries-u60ffxw0zw.pdf

Practical Trade-Offs in Integrity Protection for Binaries via Ethereum

Compression of Weather Forecast Data

The Database-as-a-Service (DaaS) paradigm addresses the outsourcing of databases to specialized storage providers, potentially reducing costs and increasing robustness. A common DaaS requirement is to prevent the storage provider from retrieving information from the outsourced data while still allowing it to execute queries. Various confidentiality preserving indexing approaches (CPIs) have been proposed that preserve confidentiality while allowing the SP to participate in query execution. However, these approaches only allow the execution of specific kinds of queries, for instance queries that select records based on the equality of a certain attribute to a search term. Choosing an optimal set of CPIs that matches the users specific requirements is a hard task, as it requires expert knowledge about both the scenario and the available CPIs. In this article, we provide an overview of the Securus framework [10] that tackles this issue. Securus allows the user to define her confidentiality needs and query workload in a Policy Profile. Securus then computes a set of CPIs that matches the specified requirements. Furthermore, a software adapter called Mediator is generated that implements the chosen CPIs and can be used to seamlessly outsource and query data.

SECURUS: Composition of Confidentiality Preserving Indexing Approaches for Secure Database-as-a-Service

A payment channel protocol does not only have to provide the payment functionality, it also has to fulfill security guarantees such as ensuring that an honest party receives their correct balance. For complexity reasons, it is typically difficult to assess the security of such a protocol or to find counterexamples in insecure protocols. In this poster, we present an approach to specify functional as well as security properties for a payment channel protocol in TLA+ and show that a Lightning Network-style protocol fulfills the required properties. In case a counterexample is found, we provide protocol developers with a graphical and intuitive output. We present the challenges we faced and our approach to meeting these challenges.

Verifying Payment Channels with TLA+

Peer-to-Peer- (P2P-) Netze bilden logische bzw. virtuelle Netze auf Basis existierender Netze wie dem Internet. P2P-Netze zeichnen sich insbesondere durch ih- re dezentrale Struktur und selbstorganisierende Mechanismen aus, welche im Gegen- satz zu Client-Server Architekturen die Last auf alle teilnehmenden Knoten gleichm¨ a- sig verteilen. Durch die dezentrale Struktur in Kombination mit selbstorganisierenden Mechanismen ist es daher m¨ oglich, hoch skalierbare P2P-Netze zu konstruieren. Zudem erhdieVerteilungauf viele Knoten dieRobustheit des Netzes gegen¨ uber Ausf¨ allen einzelner Knoten. P2P-Netze sind meist so gestaltet, dass beim Ausfall ein- zelner Knoten deren Aufgaben von einem anderen wahrgenommen werden. Dennoch sind P2P-Netze nicht per se robust, da neben dem vereinzelten Ausfall von Knoten auch gezielte Attacken m¨ oglich sind. Dieser Beitrag gibt einen ¨ Uberblick ¨ uber Atta- cken auf P2P-Netze. Auserdem wird die so genannte Sybil Attacke vertieft diskutiert und ihre Auswirkungen auf die Robustheit aufgezeigt. Abschliesend wird ein neuer Ansatz pr¨ asentiert, um die Wahrscheinlichkeit einer solchen Attacke zu verringern.

Hannes Hartenstein

Papers

Practical Trade-Offs in Integrity Protection for Binaries via Ethereum

Compression of Weather Forecast Data

SECURUS: Composition of Confidentiality Preserving Indexing Approaches for Secure Database-as-a-Service

Verifying Payment Channels with TLA+

Die vermeintliche Robustheit von Peer-to-Peer-Netzen