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1 Decentralized path-based transaction (PBT) networks maintain local payment channels between participants. Pairs of users leverage these channels to settle payments via a path of intermediaries without the need to record all transactions in a global blockchain. PBT networks such as Bitcoin's Lightning Network and Ethereum's Raiden Network are the most prominent examples of this emergent area of research. Both networks overcome scalability issues of widely used cryptocurrencies by replacing expensive and slow on-chain blockchain operations with inexpensive and fast off-chain transfers.At the core of a decentralized PBT network is a routing algorithm that discovers transaction paths between sender and receiver. In recent years, a number of routing algorithms have been proposed, including landmark routing, utilized in the decentralized IOU credit network SilentWhispers, and Flare, a link state algorithm for the Lightning Network. However, the existing efforts lack either efficiency or privacy, as well as the comprehensive analysis that is indispensable to ensure the success of PBT networks in practice. In this work, we first identify several efficiency concerns in existing routing algorithms for decentralized PBT networks. Armed with this knowledge, we design and evaluate SpeedyMurmurs, a novel routing algorithm for decentralized PBT networks using efficient and flexible embedding-based path discovery and on-demand efficient stabilization to handle the dynamics of a PBT network. Our simulation study, based on real-world data from the currently deployed Ripple credit network, indicates that SpeedyMurmurs reduces the overhead of stabilization by up to two orders of magnitude and the overhead of routing a transaction by more than a factor of two. Furthermore, using SpeedyMurmurs maintains at least the same success ratio as decentralized landmark routing, while providing lower delays. Finally, SpeedyMurmurs achieves key privacy goals for routing in decentralized PBT networks.

Peer-to-Peer (P2P) protocols usage is proliferating for a variety of applications including time-and safety-critical ones. While the distributed design of P2P provides inherent fault tolerance to certain failures, the large-scale decentralized coordination exhibits various exploitable security threats. One of these key threats are Eclipse attacks, where a large fraction of malicious peers can surround, i.e., eclipse benign peers. Topology-aware localized Eclipse attacks (taLEAs) are a new class of such attacks that allows for highly efficient denial of service attacks with a small amount of malicious resources. Our contribution is twofold: First, we show the generic susceptibility of structured P2P protocols to taLEAs. Second, we propose a new lookup mechanism for the proactive and reactive detection and mitigation of such attacks. Our novel lookup mechanism complements the common deterministic lookup with randomized decisions in order to reduce the predictability of the lookup. We validate our proposed technique via extensive simulations, increasing the lookup success to 100% in many scenarios.

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