Structured overlay networks are primarily used in data storage and data lookup, but they are vulnerable against many kinds of attacks. Within the realm of security, overlay networks have demonstrated applicability in providing privacy, availability, integrity, along with scalability. The thesis first analyses the Chord and the SALSA protocols which are organized in structured overlays to provide data with a certain degree of privacy, and then defines a new protocol called Spherical Chord which provides data lookup with privacy, while also being scalable, and addresses critical existing weaknesses in Chord and SALSA protocols. Spherical Chord is a variant of the Chord, and utilizes the concept of distributed hash table (DHT). Chord sends packets uni-directionally over a virtual id space in the overlay. While this feature provides lower latencies, it can be used by attackers to misroute and drop packets. Spherical Chord protocol introduces additional connections in the structured overlay and increases the path length and the number of paths for sending messages, hence making it more resilient to routing attacks. A new protocol focusing for constructing the Spherical Chord, followed by a new lookup protocol is defined in this thesis. The protocols are analyzed and it is demonstrated using both theoretical analysis and simulations that improved path availability helps in maintaining privacy, while also limiting the impact of routing attacks. --Abstract, page iii
