Guard: Secure routing in skip graph

Skip Graph is a distributed hash table (DHT) which acts as the underlying infrastructure in various P2P applications such as cloud storage and online social networks. The basic operation in Skip Graph is the search which is done in a fully decentralized manner. Any misbehavior of peers during the routing of a search query heavily degrades the system functionality. Security of search queries is the missing feature of Skip Graph, and applying existing DHT-based solutions on a Skip Graph reduces the search operation's efficiency and degrades the performance of query processing and response time. In this work, we propose Guard, the first fully decentralized secure search mechanism for Skip Graph, that provides authenticated and reliable search operation in a fully decentralized manner. Guard secures Skip Graph against the Sybil attack and routing attacks in the presence of the malicious colluding nodes. In contrast to the existing solutions, security of our design is formally proven.

I. Problem Definition and Motivation

Skip Graph [1] is a DHT-based routing infrastructure, which used in several P2P systems [4], [5], [2], [7], and also as an alternative infrastructure in many DHT-based services such as online social networks [9], search engines [3], and P2P storage systems [8]. In Skip Graph, each node is known by its two identifiers: numerical and name . The search for numerical ID [1], done in a fully decentralized manner, is the most common operation of Skip Graph. Nodes joining and accessibility to each other as well as their data items rely on the search for numerical ID. Any malicious behavior of nodes toward corruption of search operation directly affects the functionality of the system. Skip graph is vulnerable to routing attacks where malicious nodes try to drop, manipulate, misdirect or give the wrong reply while routing a search query, as well as the Sybil attack where a malicious node inserts an arbitrary number of fake nodes to the system to perform a large-scale attack.