Design and evaluation of persea, a sybil-resistant DHT

P2P systems are inherently vulnerable to Sybil attacks, in which an attacker creates a large number of identities and uses them to control a substantial fraction of the system. We propose Persea, a novel P2P system that derives its Sybil resistance by assigning IDs through a bootstrap tree, the graph of how nodes have joined the system through invitations. Unlike prior Sybil-resistant P2P systems based on social networks, Persea does not rely on two key assumptions: (1) that the social network is fast mixing and (2) that there is a small ratio of attack edges to honest nodes. Both assumptions have been shown to be unreliable in real social networks. A node joins Persea when it gets an invitation from an existing node in the system. The inviting node assigns a node ID to the joining node and gives it a chunk of node IDs for further distribution. For each chunk of ID space, the attacker needs to socially engineer a connection to another node already in the system. The hierarchical distribution of node IDs confines a large attacker botnet to a considerably smaller region of the ID space than in a normal P2P system. We then build upon this hierarchical ID space to make a distributed hash table (DHT) based on the Kad network. The Persea DHT uses a replication mechanism in which each (key, value) pair is stored in nodes that are evenly spaced over the network. Thus, even if a given region is occupied by attackers, the desired (key, value pair can be retrieved from other regions. We evaluate Persea in analysis and in simulations with social network datasets and show that it provides better lookup success rates than prior work with modest overheads.