Cross-layer attack and defense in cognitive radio networks

The existing research on security issues in cognitive radio networks mainly focuses on attack and defense in individual network layers. However, the attackers do not necessarily restrict themselves within the boundaries of network layers. In this paper, we design cross-layer attack strategies that can largely increase the attackers\u27 power or reducing their risk of being detected. As a case study, we investigate the coordinated report-false-sensing-data attack (PHY layer) and small-back-off-window attack (MAC layer). Furthermore, we propose a trust-based cross-layer defense framework that relies on abnormal detection in individual layers and cross-layer trust fusion. Simulation results demonstrate that the proposed defense framework can significantly reduce the maximum damage caused by attackers. ©2010 IEEE

CatchIt: Detect malicious nodes in collaborative spectrum sensing

Collaborative spectrum sensing in cognitive radio networks has been proposed as an efficient way to improve the performance of primary users detection. In collaborative spectrum sensing schemes, secondary users are often assumed to be trustworthy. In practice, however, cognitive radio nodes can be compromised. Compromised secondary users can report false detection results and significantly degrade the performance of spectrum sensing. In this paper, we investigate the case that there are multiple malicious users in cognitive radio networks and the exact number of malicious users is unknown. An onion-peeling approach is proposed to defense against multiple untrustworthy secondary nodes. We calculate suspicious level of all nodes according to their reports. When the suspicious level of a node is beyond certain threshold, it will be considered as malicious and its report will be excluded in decision-making. We continue to calculate the suspicious level of remaining nodes until no malicious node can be found. Simulation results show that malicious nodes greatly degrade the performance of collaborative sensing, and the proposed scheme can efficiently detect malicious nodes. Compared with existing defense methods, the proposed scheme significantly improves the performance of primary user detection, measured by ROC curves, and captures the dynamic change in the behaviors of malicious users

CatchIt: detect malicious nodes in collaborative spectrum sensing

Abstract-Collaborative spectrum sensing in cognitive radio networks has been proposed as an efficient way to improve the performance of primary users detection. In collaborative spectrum sensing schemes, secondary users are often assumed to be trustworthy. In practice, however, cognitive radio nodes can be compromised. Compromised secondary users can report false detection results and significantly degrade the performance of spectrum sensing. In this paper, we investigate the case that there are multiple malicious users in cognitive radio networks and the exact number of malicious users is unknown. An onion-peeling approach is proposed to defense against multiple untrustworthy secondary nodes. We calculate suspicious level of all nodes according to their reports. When the suspicious level of a node is beyond certain threshold, it will be considered as malicious and its report will be excluded in decision-making. We continue to calculate the suspicious level of remaining nodes until no malicious node can be found. Simulation results show that malicious nodes greatly degrade the performance of collaborative sensing, and the proposed scheme can efficiently detect malicious nodes. Compared with existing defense methods, the proposed scheme significantly improves the performance of primary user detection, measured by ROC curves, and captures the dynamic change in the behaviors of malicious users

doi:10.1155/2010/695750 Research Article Securing Collaborative Spectrum Sensing against Untrustworthy Secondary Users in Cognitive Radio Networks

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Cognitive radio is a revolutionary paradigm to migrate the spectrum scarcity problem in wireless networks. In cognitive radio networks, collaborative spectrum sensing is considered as an effective method to improve the performance of primary user detection. For current collaborative spectrum sensing schemes, secondary users are usually assumed to report their sensing information honestly. However, compromised nodes can send false sensing information to mislead the system. In this paper, we study the detection of untrustworthy secondary users in cognitive radio networks. We first analyze the case when there is only one compromised node in collaborative spectrum sensing schemes. Then we investigate the scenario that there are multiple compromised nodes. Defense schemes are proposed to detect malicious nodes according to their reporting histories. We calculate the suspicious level of all nodes based on their reports. The reports from nodes with high suspicious levels will be excluded in decision-making. Compared with existing defense methods, the proposed scheme can effectively differentiate malicious nodes and honest nodes. As a result, it can significantly improve the performance of collaborative sensing. For example, when there are 10 secondary users, with the primary user detection rate being equal to 0.99, one malicious user can make the false alarm rate (P f

Securing Collaborative Spectrum Sensing against Untrustworthy Secondary Users in Cognitive Radio Networks

Cognitive radio is a revolutionary paradigm to migrate the spectrum scarcity problem in wireless networks. In cognitive radio networks, collaborative spectrum sensing is considered as an effective method to improve the performance of primary user detection. For current collaborative spectrum sensing schemes, secondary users are usually assumed to report their sensing information honestly. However, compromised nodes can send false sensing information to mislead the system. In this paper, we study the detection of untrustworthy secondary users in cognitive radio networks. We first analyze the case when there is only one compromised node in collaborative spectrum sensing schemes. Then we investigate the scenario that there are multiple compromised nodes. Defense schemes are proposed to detect malicious nodes according to their reporting histories. We calculate the suspicious level of all nodes based on their reports. The reports from nodes with high suspicious levels will be excluded in decision-making. Compared with existing defense methods, the proposed scheme can effectively differentiate malicious nodes and honest nodes. As a result, it can significantly improve the performance of collaborative sensing. For example, when there are 10 secondary users, with the primary user detection rate being equal to 0.99, one malicious user can make the false alarm rate increase to 72%. The proposed scheme can reduce it to 5%. Two malicious users can make increase to 85% and the proposed scheme reduces it to 8%.</p

Attack-proof collaborative spectrum sensing in cognitive radio networks

Abstract-Collaborative sensing in cognitive radio networks can significantly improve the probability of detecting the transmission of primary users. In current collaborative sensing schemes, all collaborative secondary users are assumed to be honest. As a consequence, the system is vulnerable to attacks in which malicious secondary users report false detection results. In this paper, we investigate how to improve the security of collaborative sensing. Particularly, we develop a malicious user detection algorithm that calculates the suspicious level of secondary users based on their past reports. Then, we calculate trust values as well as consistency values that are used to eliminate the malicious users&apos; influence on the primary user detection results. Through simulations, we show that even a single malicious user can significantly degrade the performance of collaborative sensing. The proposed trust value indicator can effectively differentiate honest and malicious secondary users. The receiver operating characteristic (ROC) curves for the primary user detection demonstrate the improvement in the security of collaborative sensing

Conventional Mercury Penetration and Constant Velocity Mercury Penetration Experiments Are Used to Quantitatively Characterize the Difference in Micropore Structure in Low Permeability Reservoirs and Its Influence on Movable Fluid Saturation

There are many research methods and experimental means for quantitative and semiquantitative evaluation of low permeability reservoirs. Generally, people do not use a single means to study them but use a variety of experimental means to verify and complement each other. Conventional mercury penetration and constant velocity mercury penetration are two important experimental methods for the quantitative evaluation of tight reservoirs. The micro characteristic parameters of reservoirs obtained by them are quite different, which bring some difficulties to people’s research. This paper first analyzes the reasons for the differences between the two from the aspects of experimental theory and model, experimental conditions, and experimental process. Taking C 6 and C 7 reservoirs in Ordos Basin as an example, a total of 13 representative pairs of samples were selected to analyze the difference in capillary pressure curve shape and pore throat distribution characteristics between the two experiments and to clarify the reasons for the difference in microscopic pore characteristic parameters measured by the two experiments. Finally, the correlation between the microscopic pore characteristic parameters and the movable fluid saturation parameters is analyzed. The results show that the theoretical model of conventional mercury penetration experiment is a capillary tube bundle model with different radii. The maximum injection pressure of experimental mercury is high and the experimental speed is fast. The theoretical model of constant velocity mercury penetration experiment is the pore and throat capillary model with different radii. The maximum injection pressure is low, the experimental speed is very slow, and the process is quasistatic. The parameters such as displacement pressure, total mercury saturation, and separation coefficient obtained by the latter are smaller than those measured by the former; however, the maximum throat radius, average throat radius, and other parameters obtained by the latter are larger than those measured by the former. According to the correlation chart drawn, it can be concluded that the correlation between the microscopic pore throat characteristic parameters and the movable fluid saturation in the constant velocity mercury penetration experiment is better than that in the conventional mercury penetration experiment. The influencing factors mainly include permeability, porosity, displacement pressure, maximum pore throat radius, and sorting coefficient. The maximum mercury injection saturation has little correlation

Successful management of rare gingival metastasis from gastric adenocarcinoma: a case report and literature review

Abstract Background Gastric cancer rarely metastasizes to the oral cavity, especially to gingiva. Only 18 cases have been reported worldwide to date. This paper herein presents the nineteenth case of gingival metastasis from gastric cancer. Case presentation A 75-year-old man who underwent a radical gastrectomy for gastric adenocarcinoma was admitted to clinical oncology center for gingival mass which was originally diagnosed as epulis. The subsequent positron emission tomography-computed tomography (PET-CT) and histopathological examination revealed a gingival metastatic adenocarcinoma originated from gastric carcinoma. Then three-dimensional conformal radiotherapy (3D–CRT) with synchronization and sequential chemotherapy demonstrated clinical benefit in this patient. Furthermore, this research reviewed the records of 18 cases of gingival metastasis from gastric carcinoma in English, Japanese, and Chinese literature, and summarized the clinicopathologic features of the disease based on previously published papers. Conclusion This case suggests that gingival metastasis from gastric cancer is worthy of vigilance. Biopsy and immunohistochemical (IHC) staining should be used for the final diagnosis. Moreover, the patient with uncommon gingival metastatic lesion can be successfully treated by radiotherapy with adjuvant chemotherapy