@inproceedings{8871, author = {{Augustine, John and Ghaffari, Mohsen and Gmyr, Robert and Hinnenthal, Kristian and Kuhn, Fabian and Li, Jason and Scheideler, Christian}}, booktitle = {{Proceedings of the 31st ACM Symposium on Parallelism in Algorithms and Architectures}}, pages = {{69----79}}, publisher = {{ACM}}, title = {{{Distributed Computation in Node-Capacitated Networks}}}, doi = {{10.1145/3323165.3323195}}, year = {{2019}}, } @inbook{9599, author = {{Daymude, Joshua J. and Hinnenthal, Kristian and Richa, Andréa W. and Scheideler, Christian}}, booktitle = {{Distributed Computing by Mobile Entities, Current Research in Moving and Computing.}}, pages = {{615--681}}, publisher = {{Springer, Cham}}, title = {{{Computing by Programmable Particles}}}, doi = {{https://doi.org/10.1007/978-3-030-11072-7_22}}, year = {{2019}}, } @inproceedings{6976, abstract = {{We investigate the maintenance of overlay networks under massive churn, i.e. nodes joining and leaving the network. We assume an adversary that may churn a constant fraction $\alpha n$ of nodes over the course of $\mathcal{O}(\log n)$ rounds. In particular, the adversary has an almost up-to-date information of the network topology as it can observe an only slightly outdated topology that is at least $2$ rounds old. Other than that, we only have the provably minimal restriction that new nodes can only join the network via nodes that have taken part in the network for at least one round. Our contributions are as follows: First, we show that it is impossible to maintain a connected topology if adversary has up-to-date information about the nodes' connections. Further, we show that our restriction concerning the join is also necessary. As our main result present an algorithm that constructs a new overlay- completely independent of all previous overlays - every $2$ rounds. Furthermore, each node sends and receives only $\mathcal{O}(\log^3 n)$ messages each round. As part of our solution we propose the Linearized DeBruijn Swarm (LDS), a highly churn resistant overlay, which will be maintained by the algorithm. However, our approaches can be transferred to a variety of classical P2P Topologies where nodes are mapped into the $[0,1)$-interval.}}, author = {{Götte, Thorsten and Vijayalakshmi, Vipin Ravindran and Scheideler, Christian}}, booktitle = {{Proceedings of the 2019 IEEE 33rd International Parallel and Distributed Processing Symposium (IPDPS '19)}}, location = {{Rio de Janeiro, Brazil}}, publisher = {{IEEE}}, title = {{{Always be Two Steps Ahead of Your Enemy - Maintaining a Routable Overlay under Massive Churn with an Almost Up-to-date Adversary}}}, year = {{2019}}, } @inproceedings{10586, abstract = {{We consider the problem of transforming a given graph G_s into a desired graph G_t by applying a minimum number of primitives from a particular set of local graph transformation primitives. These primitives are local in the sense that each node can apply them based on local knowledge and by affecting only its 1-neighborhood. Although the specific set of primitives we consider makes it possible to transform any (weakly) connected graph into any other (weakly) connected graph consisting of the same nodes, they cannot disconnect the graph or introduce new nodes into the graph, making them ideal in the context of supervised overlay network transformations. We prove that computing a minimum sequence of primitive applications (even centralized) for arbitrary G_s and G_t is NP-hard, which we conjecture to hold for any set of local graph transformation primitives satisfying the aforementioned properties. On the other hand, we show that this problem admits a polynomial time algorithm with a constant approximation ratio.}}, author = {{Scheideler, Christian and Setzer, Alexander}}, booktitle = {{Proceedings of the 46th International Colloquium on Automata, Languages, and Programming}}, keywords = {{Graphs transformations, NP-hardness, approximation algorithms}}, location = {{Patras, Greece}}, pages = {{150:1----150:14}}, publisher = {{Dagstuhl Publishing}}, title = {{{On the Complexity of Local Graph Transformations}}}, doi = {{10.4230/LIPICS.ICALP.2019.150}}, volume = {{132}}, year = {{2019}}, } @inproceedings{12944, author = {{Götte, Thorsten and Hinnenthal, Kristian and Scheideler, Christian}}, booktitle = {{Structural Information and Communication Complexity}}, title = {{{Faster Construction of Overlay Networks}}}, doi = {{10.1007/978-3-030-24922-9_18}}, year = {{2019}}, } @inproceedings{15627, author = {{Augustine, John and Hinnenthal, Kristian and Kuhn, Fabian and Scheideler, Christian and Schneider, Philipp}}, booktitle = {{Proceedings of the Fourteenth Annual ACM-SIAM Symposium on Discrete Algorithms}}, isbn = {{9781611975994}}, pages = {{1280--1299}}, title = {{{Shortest Paths in a Hybrid Network Model}}}, doi = {{10.1137/1.9781611975994.78}}, year = {{2019}}, } @article{14830, author = {{Gmyr, Robert and Lefevre, Jonas and Scheideler, Christian}}, journal = {{Theory Comput. Syst.}}, number = {{2}}, pages = {{177--199}}, title = {{{Self-Stabilizing Metric Graphs}}}, doi = {{10.1007/s00224-017-9823-4}}, volume = {{63}}, year = {{2019}}, } @inproceedings{14539, author = {{Castenow, Jannik and Kolb, Christina and Scheideler, Christian}}, booktitle = {{Proceedings of the 26th International Colloquium on Structural Information and Communication Complexity (SIROCCO)}}, location = {{L'Aquila, Italy}}, pages = {{345--348}}, title = {{{A Bounding Box Overlay for Competitive Routing in Hybrid Communication Networks}}}, doi = {{10.1007/978-3-030-24922-9\_26}}, year = {{2019}}, } @inproceedings{13182, abstract = {{We consider congestion control in peer-to-peer distributed systems. The problem can be reduced to the following scenario: Consider a set $V$ of $n$ peers (called \emph{clients} in this paper) that want to send messages to a fixed common peer (called \emph{server} in this paper). We assume that each client $v \in V$ sends a message with probability $p(v) \in [0,1)$ and the server has a capacity of $\sigma \in \mathbb{N}$, i.e., it can recieve at most $\sigma$ messages per round and excess messages are dropped. The server can modify these probabilities when clients send messages. Ideally, we wish to converge to a state with $\sum p(v) = \sigma$ and $p(v) = p(w)$ for all $v,w \in V$. We propose a \emph{loosely} self-stabilizing protocol with a slightly relaxed legitimate state. Our protocol lets the system converge from \emph{any} initial state to a state where $\sum p(v) \in \left[\sigma \pm \epsilon\right]$ and $|p(v)-p(w)| \in O(\frac{1}{n})$. This property is then maintained for $\Omega(n^{\mathfrak{c}})$ rounds in expectation. In particular, the initial client probabilities and server variables are not necessarily well-defined, i.e., they may have arbitrary values. Our protocol uses only $O(W + \log n)$ bits of memory where $W$ is length of node identifiers, making it very lightweight. Finally we state a lower bound on the convergence time an see that our protocol performs asymptotically optimal (up to some polylogarithmic factor). }}, author = {{Feldmann, Michael and Götte, Thorsten and Scheideler, Christian}}, booktitle = {{Proceedings of the 21st International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS)}}, pages = {{149--164}}, publisher = {{Springer, Cham}}, title = {{{A Loosely Self-stabilizing Protocol for Randomized Congestion Control with Logarithmic Memory}}}, doi = {{https://doi.org/10.1007/978-3-030-34992-9_13}}, year = {{2019}}, } @inproceedings{13652, author = {{Hinnenthal, Kristian and Scheideler, Christian and Struijs, Martijn}}, booktitle = {{33rd International Symposium on Distributed Computing (DISC 2019)}}, title = {{{Fast Distributed Algorithms for LP-Type Problems of Low Dimension}}}, doi = {{10.4230/LIPICS.DISC.2019.23}}, year = {{2019}}, } @inproceedings{3422, abstract = {{We study the consensus problem in a synchronous distributed system of n nodes under an adaptive adversary that has a slightly outdated view of the system and can block all incoming and outgoing communication of a constant fraction of the nodes in each round. Motivated by a result of Ben-Or and Bar-Joseph (1998), showing that any consensus algorithm that is resilient against a linear number of crash faults requires $\tilde \Omega(\sqrt n)$ rounds in an n-node network against an adaptive adversary, we consider a late adaptive adversary, who has full knowledge of the network state at the beginning of the previous round and unlimited computational power, but is oblivious to the current state of the nodes. Our main contributions are randomized distributed algorithms that achieve consensus with high probability among all except a small constant fraction of the nodes (i.e., "almost-everywhere'') against a late adaptive adversary who can block up to ε n$ nodes in each round, for a small constant ε >0$. Our first protocol achieves binary almost-everywhere consensus and also guarantees a decision on the majority input value, thus ensuring plurality consensus. We also present an algorithm that achieves the same time complexity for multi-value consensus. Both of our algorithms succeed in $O(log n)$ rounds with high probability, thus showing an exponential gap to the $\tilde\Omega(\sqrt n)$ lower bound of Ben-Or and Bar-Joseph for strongly adaptive crash-failure adversaries, which can be strengthened to $\Omega(n)$ when allowing the adversary to block nodes instead of permanently crashing them. Our algorithms are scalable to large systems as each node contacts only an (amortized) constant number of peers in each communication round. We show that our algorithms are optimal up to constant (resp.\ sub-logarithmic) factors by proving that every almost-everywhere consensus protocol takes $\Omega(log_d n)$ rounds in the worst case, where d is an upper bound on the number of communication requests initiated per node in each round. We complement our theoretical results with an experimental evaluation of the binary almost-everywhere consensus protocol revealing a short convergence time even against an adversary blocking a large fraction of nodes.}}, author = {{Robinson, Peter and Scheideler, Christian and Setzer, Alexander}}, booktitle = {{Proceedings of the 30th ACM Symposium on Parallelism in Algorithms and Architectures (SPAA)}}, isbn = {{978-1-4503-5799-9/18/07}}, keywords = {{distributed consensus, randomized algorithm, adaptive adversary, complexity lower bound}}, location = {{Wien}}, title = {{{Breaking the $\tilde\Omega(\sqrt{n})$ Barrier: Fast Consensus under a Late Adversary}}}, doi = {{10.1145/3210377.3210399}}, year = {{2018}}, } @inproceedings{1163, abstract = {{In this paper we present two major results: First, we introduce the first self-stabilizing version of a supervised overlay network (as introduced in~\cite{DBLP:conf/ispan/KothapalliS05}) by presenting a self-stabilizing supervised skip ring. Secondly, we show how to use the self-stabilizing supervised skip ring to construct an efficient self-stabilizing publish-subscribe system. That is, in addition to stabilizing the overlay network, every subscriber of a topic will eventually know all of the publications that have been issued so far for that topic. The communication work needed to processes a subscribe or unsubscribe operation is just a constant in a legitimate state, and the communication work of checking whether the system is still in a legitimate state is just a constant on expectation for the supervisor as well as any process in the system. }}, author = {{Feldmann, Michael and Kolb, Christina and Scheideler, Christian and Strothmann, Thim Frederik}}, booktitle = {{Proceedings of the 32nd IEEE International Parallel & Distributed Processing Symposium (IPDPS)}}, keywords = {{Topological Self-stabilization, Supervised Overlay, Publish-Subscribe System}}, location = {{Vancouver}}, publisher = {{IEEE}}, title = {{{Self-Stabilizing Supervised Publish-Subscribe Systems}}}, doi = {{10.1109/IPDPS.2018.00114}}, year = {{2018}}, } @inproceedings{1164, abstract = {{We propose a distributed protocol for a queue, called Skueue, which spreads its data fairly onto multiple processes, avoiding bottlenecks in high throughput scenarios. Skueuecan be used in highly dynamic environments, through the addition of join and leave requests to the standard queue operations enqueue and dequeue. Furthermore Skueue satisfies sequential consistency in the asynchronous message passing model. Scalability is achieved by aggregating multiple requests to a batch, which can then be processed in a distributed fashion without hurting the queue semantics. Operations in Skueue need a logarithmic number of rounds w.h.p. until they are processed, even under a high rate of incoming requests.}}, author = {{Feldmann, Michael and Scheideler, Christian and Setzer, Alexander}}, booktitle = {{Proceedings of the 32nd IEEE International Parallel & Distributed Processing Symposium (IPDPS)}}, location = {{Vancouver}}, publisher = {{IEEE}}, title = {{{Skueue: A Scalable and Sequentially Consistent Distributed Queue}}}, doi = {{10.1109/IPDPS.2018.00113}}, year = {{2018}}, } @article{1796, author = {{J. Daymude, Joshua and Derakhshandeh, Zahra and Gmyr, Robert and Porter, Alexandra and W. Richa, Andrea and Scheideler, Christian and Strothmann, Thim Frederik}}, journal = {{Natural Computing}}, number = {{1}}, pages = {{81----96}}, title = {{{On the runtime of universal coating for programmable matter}}}, doi = {{10.1007/s11047-017-9658-6}}, year = {{2018}}, } @inproceedings{5764, author = {{Gmyr, Robert and Hinnenthal, Kristian and Kostitsyna, Irina and Kuhn, Fabian and Rudolph, Dorian and Scheideler, Christian and Strothmann, Thim Frederik}}, booktitle = {{Proceedings of the 24th International Conference on DNA Computing and Molecular Programming}}, pages = {{122--138}}, publisher = {{Springer International Publishing}}, title = {{{Forming Tile Shapes with Simple Robots}}}, doi = {{10.1007/978-3-030-00030-1_8}}, year = {{2018}}, } @techreport{5820, abstract = {{In this paper, we investigate the use of trusted execution environments (TEEs, such as Intel's SGX) for an anonymous communication infrastructure over untrusted networks. For this, we present the general idea of exploiting trusted execution environments for the purpose of anonymous communication, including a continuous-time security framework that models strong anonymity guarantees in the presence of an adversary that observes all network traffic and can adaptively corrupt a constant fraction of participating nodes. In our framework, a participating node can generate a number of unlinkable pseudonyms. Messages are sent from and to pseudonyms, allowing both senders and receivers of messages to remain anonymous. We introduce a concrete construction, which shows viability of our TEE-based approach to anonymous communication. The construction draws from techniques from cryptography and overlay networks. Our techniques are very general and can be used as a basis for future constructions with similar goals.}}, author = {{Blömer, Johannes and Bobolz, Jan and Scheideler, Christian and Setzer, Alexander}}, title = {{{Provably Anonymous Communication Based on Trusted Execution Environments}}}, year = {{2018}}, } @article{5984, author = {{Scheideler, Christian}}, journal = {{Theor. Comput. Sci.}}, pages = {{1}}, title = {{{Preface}}}, doi = {{10.1016/j.tcs.2018.11.004}}, volume = {{751}}, year = {{2018}}, } @inproceedings{5985, author = {{Scheideler, Christian}}, booktitle = {{Proceedings of the 2018 Workshop on Theory and Practice for Integrated Cloud, Fog and Edge Computing Paradigms, TOPIC@PODC 2018, Egham, United Kingdom, July 27, 2018}}, pages = {{1--2}}, title = {{{Relays: Towards a Link Layer for Robust and Secure Fog Computing}}}, doi = {{10.1145/3229774.3229781}}, year = {{2018}}, } @inproceedings{5986, author = {{Gmyr, Robert and Hinnenthal, Kristian and Kostitsyna, Irina and Kuhn, Fabian and Rudolph, Dorian and Scheideler, Christian}}, booktitle = {{43rd International Symposium on Mathematical Foundations of Computer Science, MFCS 2018, August 27-31, 2018, Liverpool, UK}}, pages = {{52:1--52:15}}, title = {{{Shape Recognition by a Finite Automaton Robot}}}, doi = {{10.4230/LIPIcs.MFCS.2018.52}}, year = {{2018}}, } @inproceedings{4411, abstract = {{While a lot of research in distributed computing has covered solutions for self-stabilizing computing and topologies, there is far less work on self-stabilization for distributed data structures. Considering crashing peers in peer-to-peer networks, it should not be taken for granted that a distributed data structure remains intact. In this work, we present a self-stabilizing protocol for a distributed data structure called the hashed Patricia Trie (Kniesburges and Scheideler WALCOM'11) that enables efficient prefix search on a set of keys. The data structure has a wide area of applications including string matching problems while offering low overhead and efficient operations when embedded on top of a distributed hash table. Especially, longest prefix matching for $x$ can be done in $\mathcal{O}(\log |x|)$ hash table read accesses. We show how to maintain the structure in a self-stabilizing way. Our protocol assures low overhead in a legal state and a total (asymptotically optimal) memory demand of $\Theta(d)$ bits, where $d$ is the number of bits needed for storing all keys.}}, author = {{Knollmann, Till and Scheideler, Christian}}, booktitle = {{Proceedings of the 20th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS)}}, editor = {{Izumi, Taisuke and Kuznetsov, Petr}}, keywords = {{Self-Stabilizing, Prefix Search, Distributed Data Structure}}, location = {{Tokyo}}, publisher = {{Springer, Cham}}, title = {{{A Self-Stabilizing Hashed Patricia Trie}}}, doi = {{10.1007/978-3-030-03232-6_1}}, volume = {{11201}}, year = {{2018}}, }