機會網路（Opportunistic Networks）是一種由多個行動節點組合而成的新興網路型態。這些節點會分享彼此的資料和資源，或是彼此合作提供各種服務，如資料轉傳。一般而言，機會網路中的節點藉由機率式的接觸建立連線，因此其連線通常是間歇性的。由於無法利用從網際網路所提供的現有安全機制去驗證節點提供的服務，機會網路上將衍生兩種信任的議題，資料信任與行動信任。資料信任的議題主要源自於惡意或錯誤的資料可能對節點造成傷害，而行動信任的議題則是由於節點有限的能力或個人特性造成節點的自私行為。
為了解決這兩種信任的議題，本篇論文提出了適用於機會網路的信任評估方法。資料信任評估方法採用與現有方法不同的概念，其利用持有此資料的節點的個人檔案，如興趣，來判斷資料的正確性。而行動信任評估方法為了避免採用來自網際網路的資料起源紀錄，特別考量了節點的聲望與動機。藉此，本論文所提之行動信任評估方式可以準確且有效的評估一個節點的可信賴程度，並改善傳統聲望系統可能遭受的冷起始問題(Cold start problem)。
由實驗結果顯示，我們的資料信任評估方式比傳統多數決的方式更能準確的驗證網路中資料的正確性。而在行動信任評估方法中，我們也藉由實驗驗證了其概念的正確性。因此，本論文提出之信任評估方式可以有效的運用於評估機會網路中節點和資料的可信程度。

Opportunistic networks are emerging network environments composed of several mobile nodes. These nodes might share their data and resources, or cooperate with others to provide various services, such as data forwarding. Generally, the connectivity in opportunistic networks is always intermittent because communications between nodes are achieved by their opportunistic contacts. Since existing security mechanisms from Internet cannot be exploited to verify services provided by mobile nodes, two kinds of trust issues, data trust and action trust, therefore arise. The data trust issue indicates that malicious or incorrect data might damage the carried nodes, and the action trust issue is mainly caused by the selfish behavior of nodes due to limited resources or characteristics of nodes.
In this thesis, trust evaluation methods for opportunistic networks are proposed to deal with the data trust and action trust problems. The proposed data trust evaluation method presents a novel concept to estimate the data trust based on the profiles of carried nodes, such as interests, and it is thoroughly different from existing methods. The proposed action trust evaluation method assesses node credibility without the supports of provenance repositories from Internet. By considering the reputation as well as intention of nodes, the action trust of nodes can be evaluated accurately and efficiently whereas alleviating the cold start problem inherited from traditional reputation-based system.
The experiment results show that the proposed data trust evaluation method provides better accuracy than majority-based methods in verifying the data correctness. The experiment results of the action trust evaluation method prove the validness of concepts used by the proposed method. Thus, the proposed trust evaluation methods for opportunistic networks are effective.

Adali, S., Escriva, R., Goldberg, M., Hayvanovych, M., Magdon-Ismail, M., Szymanski, B., . . . Williams, G. (May 23-26, 2010). Measuring Behavioral Trust in Social Networks. Intelligence and Security Informatics, (pp. 150-152). Vancouver, BC.
Buchegger, S., & Le Boudec, J.-Y. (March 3-5, 2003). The Effect of Rumor Spreading in Reputation Systems for Mobile Ad-Hoc Networks. Proceedings of the Workshop on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks, (pp. 131-140). INRIA Sophia-Antipolis, France.
Chen, T., & Venkataramanan, V. (2005, November-December). Dempster-Shafer Theory for Intrusion Detection in Ad Hoc Networks. Internet Computing, IEEE, 9(6), pp. 35-41.
Flagg, R. (2013, April 23). Basics of Survey and Question Design. Retrieved June 24, 2013, from HowTo.gov | Helping agencies deliver a great customer experience: http://www.howto.gov/customer-experience/collecting-feedback/basics-of-survey-and-question-design
Guy, I., Avraham, U., Carmel, D., Ur, S., Jacovi, M., & Ronen, I. (May 13-17, 2013). Mining Expertise and Interests from Social Media. The International World Wide Web Conference, (pp. 515-526). Rio de Janeiro, Brazil.
Huang, D., Zhou, Z., Hong, X., & Gerla, M. (January 9-12, 2010). Establishing Email-Based Social Network Trust for Vehicular Networks. IEEE Consumer Communications and Networking Conference, (pp. 1-5). Las Vegas, NV, USA.
Jetton, T., & Alexander, P. (2001, September). Interest Assessment and the Content Area Literacy Environment: Challenges for Research and Practice. Educational Psychology Review, 13(3), pp. 303-318.
Konorski, J., & Orlikowski, R. (December 20-23, 2009). Data-Centric Dempster-Shafer Theory-Based Selfishness Thwarting via Trust Evaluation in MANETs and WSNs. New Technologies, Mobility and Security, (pp. 1-5). Cairo, Egypt.
Li, M., Hu, J., & Du, J. (August 10-12, 2010). A Data-Centric Trust Evaluation Mechanism in Wireless Sensor Networks. Distributed Computing and Applications to Business Engineering and Science, (pp. 466-470). Hong Kong, China.
McDaniel, P. (2011, March-April). Data Provenance and Security. IEEE Security & Privacy, 9(2), pp. 83-85.
Moossavizadeh, S. M., Mohsenzadeh, M., & Arshadi, N. (2012, July). A New Approach to Measure Believability Dimension of Data Quality. Management Science Letters, 2(7), pp. 2565-2570.
Mtibaa, A., & Harras, K. (July 31 - August 4, 2011). Social-Based Trust in Mobile Opportunistic Networks. The International Conference on Computer Communications and Networks, (pp. 1-6). Maui, Hawaii.
Pelusi, L., Passarella, A., & Marco, C. (2006, November). Opportunistic Networking: Data Forwarding in Disconnected Mobile Ad Hoc Networks. IEEE Communications Magazine, 44(11), 134-141.
Prat, N., & Madnick, S. E. (January 7-10, 2008). Measuring Data Believability: A Provenance Approach. Hawaii International Conference on System Sciences, (pp. 393-393). Waikoloa, Big Island, Hawaii.
Raya, M., Papadimitratos, P., Gligor, V., & Hubaux, , J.-P. (April 13-18, 2008). On Data-Centric Trust Establishment in Ephemeral Ad Hoc Networks. IEEE International Conference on Computer Communications, (pp. 1238-1246). Phoenix, AZ, U.S.A.
Sidi, F., Shariat Panahy, P., Affendey, L., Jabar, M., Ibrahim, H., & Mustapha, A. (March 13-15, 2012). Data Quality: A Survey of Data Quality Dimensions. International Conference on Information Retrieval & Knowledge Management, (pp. 300-304). Kuala Lumpur, Malaysia.
Sun, Y. L., Yu, W., Han, Z., & Liu, K. R. (2006, September). Information Theoretic Framework of Trust Modeling and Evaluation for Ad Hoc Networks. IEEE Journal on Selected Areas in Communications, 24(2), pp. 305-317.
Taylor-Powell, E. (May 1998). Questionnaire Design: Asking Questions with a Purpose. Wisconsin, U.S.A.: University of Wisconsin - Extension.
Tobias, S. (1994, Spring). Interest, Prior Knowledge, and Learning. Review of Educational Research, 64(1), pp. 37-54.
Trifunovic, S., Legendre, F., & Anastasiades, C. (March 15-19, 2010). Social Trust in Opportunistic Networks. IEEE Conference on Computer Communications Workshops, (pp. 1-6). San Diego, U.S.A.
Wang, Y.-Y. R., & Strong, D. M. (1996, March). Beyond Accuracy: What Data Quality Means to Data Consumers. Journal of Management Information Systems, 12(4), pp. 5-33.
Yu, H., Shen, Z., Miao, C., Leung, C., & Niyato, D. (2010, October). A Survey of Trust and Reputation Management Systems in Wireless Communications. 98(10), pp. 1755-1772.