People are constantly using mobile technologies to exchange perspectives across the world. The search services they use, however, belong to centralized systems that may be easily censored. The Peer-to-Peer retrieval system was created to impede censorship of online information, but the decentralized nature of P2P makes it difficult to infer information that cannot be measured directly, such as the proportion of subversion, selfish nodes, network size, or churn rate. Recent advances have pushed providers toward large-scale wireless networks where data retrieval is difficult. Thus, we propose a defense mechanism that can: (1) tackle censorship issues; (2) employ probability density function, exponential weighted moving average and modified Chi-squared tests to estimate the proportion of malicious and selfish nodes; (3) defend against malicious and selective-forwarding attacks by adjusting the number of forwarding levels and requests to ensure high-match probability; (4) maintain high-retrieval rates even in large and highly mobile networks; and (5) guarantee robustness compared to other search systems. A series of experiments demonstrated our algorithm’s high-retrieval rate, reasonable costs, mobility resilience, and robustness, demonstrating that the algorithm can work well when the network size is large and/or has a large proportion of selfish nodes, malicious nodes and mobile nodes.

The iTrust system is a decentralized and distributed publication, search and retrieval system that makes it difficult to censor or filter information accessed over the Internet. iTrust employs a completely distributed membership algorithm, and a detection and defensive adaptation algorithm that protects against malicious nodes in the membership. These algorithms depend on information that cannot be observed or measured directly, the current size of the membership and the current proportion of malicious nodes in the membership. They use statistical estimation to approximate these network environment parameters, and then they dynamically adapt accordingly. These algorithms provide accurate and timely management of the iTrust system in the presence of membership churn and malicious nodes.

Abstract The iTrust search and retrieval network is designed to impede attempts to censor or filter information accessed over the Internet, providing trustworthy access to information on the Web. In iTrust, a fully distributed membership algorithm and a detection/defensive adaptation algorithm act in concert to protect against malicious nodes in membership. By applying statistical inference for both detection and defensive algorithms, I was able to measure information that cannot be observed directly, such as the current size of the membership and the current proportion of malicious nodes in the network. Experimentation demonstrates that both algorithms are able to estimate these metrics quickly and accurately, to the point that the nodes can use them to manage the iTrust system, despite a high rate of membership churn, a large number of malicious nodes, and a mere partial view of network membership. Copyright © 2015 John Wiley & Sons, Ltd.

This paper describes the iTrust over SMS decentralized search and retrieval system for mobile networks. Any mobile device in the iTrust network can communicate with any other mobile device in the iTrust network to distribute, search for, and retrieve information. Third-party developers can use the iTrust over SMS API on the Android platform to add this search and retrieval functionality to existing applications quickly and easily. Developers of applications for other mobile device platforms can use the iTrust over SMS protocol to create compatible applications that can communicate using iTrust over SMS. In addition to the iTrust over SMS components and protocol, this paper presents a performance evaluation of the iTrust over SMS system, which shows that the probability of information retrieval is high, even if some of the mobile devices are not available. It also shows that the average search latency is consistently less if all of the participating nodes use the same mobile service provider, and is consistently more if the nodes use different mobile service providers.