Current leader election algorithms fail in the presence of Sybil attacks, i.e., one malicious entity inserting many nodes, network dynamics, and restricted knowledge about the graph. However, social overlay networks, i.e., peer-to-peer networks with links corresponding to social relationships, face all of the above challenges. Social overlay networks naturally offer privacy, as they avoid connections with strangers, and furthermore prevent a Sybil attacker from controlling a large number of links in the graph. As recent ideas for scalable communication in such overlays rely heavily on attack resistant leader election, solving leader election for such overlays opens the door for decentralized, privacy-preserving, and secure communication at a large scale.In this work, we propose a novel leader election algorithm based on three-majority voting that utilizes timestamps and cryptographic signatures to detect leader faults in an attack resistant manner. We evaluate our algorithm with simulations on real-world as well as synthetic network topologies. Our results indicate that in networks whose degree sequence follows a power law, our leader election algorithm quickly achieves consensus for more than 80% of all nodes. Furthermore, attackers are unlikely to become leaders as long as the number of connections they establish with honest nodes is low.

Nodes in route-restricted overlays have an immutable set of neighbors, explicitly specified by their users. Popular examples include payment networks such as the Lightning network as well as social overlays such as the Dark Freenet. Routing algorithms are central to such overlays as they enable communication between nodes that are not directly connected. Recent results show that algorithms based on spanning trees are the most promising provably efficient choice. However, all suggested solutions fail to address how distributed spanning tree algorithms can deal with active denial of service attacks by malicious nodes.In this work, we design a novel self-stabilizing spanning tree construction algorithm that utilizes cryptographic signatures and prove that it reduces the set of nodes affected by active attacks. Our simulations substantiate this theoretical result with concrete values based on real-world data sets. In particular, our results indicate that our algorithm reduces the number of affected nodes by up to 74% compared to state-of-the-art attack-resistant spanning tree constructions.

Balancing the load in content addressing schemes for route-restricted networks represents a challenge with a wide range of applications. Solutions based on greedy embeddings maintain minimal state information and enable efficient routing, but any such solutions currently result in either imbalanced content addressing, overloading individual nodes, or are unable to efficiently account for network dynamics.In this work, we propose a greedy embedding in combination with a content addressing scheme that provides balanced content addressing while at the same time enabling efficient stabilization in the presence of network dynamics. We point out the tradeoff between stabilization complexity and maximal permitted imbalance when deriving upper bounds on both metrics for two variants of the proposed algorithms. Furthermore, we substantiate these bounds through a simulation study based on both real-world and synthetic data.

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