This paper addresses the security issues in structured peer-to-peer (p2p) overlay networks, which are crucial for large-scale decentralized applications such as distributed storage, group communication, and content distribution. The authors identify attacks that can prevent correct message delivery and propose defenses to these attacks. They focus on secure routing, which involves secure node identifier assignment, routing table maintenance, and message forwarding. The paper presents techniques to maintain secure routing even in the presence of malicious nodes, demonstrating that the overhead of secure routing is acceptable and proportional to the fraction of malicious nodes. The authors also discuss the use of self-certifying data to minimize the overhead of secure routing. The paper includes a detailed analysis of attacks and solutions, with a specific focus on the Pastry overlay protocol, and evaluates the effectiveness of the proposed techniques through simulations.This paper addresses the security issues in structured peer-to-peer (p2p) overlay networks, which are crucial for large-scale decentralized applications such as distributed storage, group communication, and content distribution. The authors identify attacks that can prevent correct message delivery and propose defenses to these attacks. They focus on secure routing, which involves secure node identifier assignment, routing table maintenance, and message forwarding. The paper presents techniques to maintain secure routing even in the presence of malicious nodes, demonstrating that the overhead of secure routing is acceptable and proportional to the fraction of malicious nodes. The authors also discuss the use of self-certifying data to minimize the overhead of secure routing. The paper includes a detailed analysis of attacks and solutions, with a specific focus on the Pastry overlay protocol, and evaluates the effectiveness of the proposed techniques through simulations.