The Dynamics of Salsa: A Robust Structured P2P System

Salsa is a structured peer-to-peer system that is designed to perform robust and reliable lookups. It uses a distributed hash table based on hashes of the nodes’ IP addresses to organize the nodes into groups. With a virtual tree structure, limited knowledge of other nodes is enough to route lookups throughout the system. We use redundancy and bounds checking when performing lookups to prevent malicious nodes from returning false information without detection. We show that our scheme prevents attackers from biasing lookups, while incurring moderate overheads, as long as the fraction of malicious nodes is less than 20%. The number of groups can be used as a tunable parameter to trade-off performance versus security. Salsa is resilient to nodes joining and leaving the system while node lookups are ongoing. The message overhead for system operations in a dynamic network is minimal, with the highest measured message overhead of 0.04 messages per node per minute in simulation time.