The quality of peer-to-peer networks using network coding can suffer when nodes will not encode packets and malicious nodes intentionally corrupt the encoded packets. In this situation, nodes should be stimulated to cooperate with each other, and malicious nodes are also need to be detected. We propose an incentive scheme which not only stimulates the nodes encoding the data packets, but also stimulates the nodes sharing the alert messages when a malicious packet is found.

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The reward of the Bitcoin system is designed to be proportional to miner's computational power. However, rogue miners can increase their rewards by using the block withholding attacks. For raising awareness on the Bitcoin reward system, a new attack scheme is proposed, where the attackers infiltrate into an open pool and launch the

mining as well as the block withholding attack. The simulation results demonstrate that the proposed attack outperforms the conventional block withholding attacks.

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Recent studies revealed that some social and technological network formations can be represented by the network formation games played by multiple agents. In general, the topologies formed by multiple agents are worse than or equal to those formed by the centralized designer in the sense of social total welfare. Several works such as the price of anarchy are known as a measure for evaluating the inefficiency of solutions obtained by multiple agents compared to the social optimal solution. In this paper, we introduce the expected price of anarchy which is proposed as a valid measure for evaluating the inefficiency of the dynamic network formation game whose solution space is divided into basins with multimodal sizes. Moreover, through some computer simulations we show that it can represent the average case behavior of inefficiency of dynamic network formation games which is missed by two previous measures.

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Recent studies revealed that some social and technological network formations can be represented by the network formation games played by multiple agents. In general, the topologies formed by multiple agents are worse than or equal to those formed by the centralized designer in the sense of social total welfare. Several works such as the price of anarchy are known as a measure for evaluating the inefficiency of solutions obtained by multiple agents compared to the social optimal solution. In this paper, we introduce the expected price of anarchy which is proposed as a valid measure for evaluating the inefficiency of the dynamic network formation game whose solution space is divided into basins with multimodal sizes. Moreover, through some computer simulations we show that it can represent the average case behavior of inefficiency of dynamic network formation games which is missed by two previous measures.

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本研究では，日本，米国，中国で実施したインターネット実験を通して，観察的学習が被験者の社会規範意識へ与える影響について分析する．実験結果によれば，他人の行動についての観察的学習を行う場合には，被験者の行動は同調的に変化するだけでなく，非同調的にも変化することが観察された．また，他人への同調行動·非同調行動は，それぞれ異なる要因によって引き起こされることが確認された．

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The present study aims to investigate when and why helping behaviors are criticized by a third party. We propose that people infer an ulterior

motive for others’ helping behaviors that occur in some self-presentational contexts. A vignette study was conducted with 149 undergraduates who read scenarios describing helping behaviors in various kinds of contexts. Analysis using a multi-level structural equation model provided partial support for our notion. It was shown that motives were more likely inferred in situations in which observers who happened to be there praised the helping behavior than otherwise. However, this did not lead to increased criticism. It was also shown that the help was more likely regarded as needless, and, therefore, motives were more strongly inferred when the help was refused than when it was requested by a recipient. Some methodological problems and future directions are discussed.

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Due to the lack of end-to-end paths between the communication source and destination, the routing of Delay Tolerant Networks (DTN) exploits the store-carry-and-forward mechanism. This mechanism requires nodes with sufficient energy to relay and forward messages in a cooperative and selfless way. However, in the real world, the energy is constrained and most of the nodes exhibit behaviors. In this paper, we investigate the performance of DTN routing schemes considering both the energy constraint and behaviors of nodes. First, we model the two-hop relay and epidemic routing based on a two-dimensional continuous time Markov chain. Then, we obtain the system performance of message delivery delay and delivery cost by explicit expressions. Numerical results show that both the energy constraint and node selfishness reduce the message delivery cost at the expense of increasing the message delivery delay. Furthermore, we demonstrate that the energy constraint plays a more important role in the performance of epidemic routing than that of two-hop relay.

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This study examined the influence of motivation ( or altruistic) and social relationships (friend or acquaintance) on evaluations of morality and personality of liars. Participants (N = 163) read scenarios in which an actor made one of four referent statements ( lie, altruistic lie, truth or altruistic truth), and then evaluated his/her morality (honesty and benevolence) and personality (Extroversion, Agreeableness, Conscientiousness, Neuroticism, and Openness to experience). The results showed that: a) liars were evaluated lower in honesty and Conscientiousness than truthtellers; b) altruistic liars were evaluated higher in benevolence and Agreeableness than liars as well as truth-tellers; and c) altruistic liars were evaluated higher in Neuroticism and lower in Extroversion than truth-tellers. This study offered new insights on how people evaluate liars.

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The necessary cooperation in packet forwarding by wireless mobile ad hoc network users can be achieved if nodes create a distributed cooperation enforcement mechanism. One of the most significant roles in this mechanism is played by a trust system, which enables forwarding nodes to distinguish between cooperative (therefore trustworthy) and (untrustworthy) nodes. As shown in this paper, the performance of the system depends on the data classes describing the forwarding behaviour of nodes, which are used for the evaluation of their level of cooperation. The paper demonstrates that partition of such data into personal and general classes can help to create better protection against clique-building among nodes. Personal data takes into account the status of packets originated by a node itself, while general considers the status of packets originated by other nodes. Computational experiments demonstrate that, in the presence of a large number of and colluding nodes, prioritising the personal data improves the performance of cooperative nodes and creates a better defence against colluding free-riders.

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The necessary cooperation in packet forwarding by wireless mobile ad hoc network users can be achieved if nodes create a distributed cooperation enforcement mechanism. One of the most significant roles in this mechanism is played by a trust system, which enables forwarding nodes to distinguish between cooperative (therefore trustworthy) and (untrustworthy) nodes. As shown in this paper, the performance of the system depends on the data classes describing the forwarding behaviour of nodes, which are used for the evaluation of their level of cooperation. The paper demonstrates that partition of such data into personal and general classes can help to create better protection against clique-building among nodes. Personal data takes into account the status of packets originated by a node itself, while general considers the status of packets originated by other nodes. Computational experiments demonstrate that, in the presence of a large number of and colluding nodes, prioritising the personal data improves the performance of cooperative nodes and creates a better defence against colluding free-riders.

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A routing game is a simple model of behaviors in networks. It is called that Braess's paradox occurs in the routing game if an equilibrium flow achieved by players' behaviors is not the optimal minimum latency flow. In order to make the minimum latency flow a Nash equilibrium, a marginal cost tax has been proposed. Braess graphs have also been proposed to discuss Braess's paradox. In a large population of players, conflicts between purposes of each player and the population causes social dilemmas. In game theory, to resolve the social dilemmas, a capitation tax and/or a subsidy has been introduced, and players' dynamical behaviors have been formulated by replicator dynamics. In this paper, we formulate replicator dynamics in the Braess graphs and investigate stability of the minimum latency flow with and without the marginal cost tax. An additional latency caused by the marginal cost tax is also shown. To resolve the problem of the additional latency, we extend the capitation tax and the subsidy to a state-dependent tax and apply it to the stabilization problem of the minimum latency flow.

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The security of P2P networks depends on building trust management among peers. However, current trust management models focus on preventing untrustworthy resources from spreading by malicious providers, but have few effects on reducing denial-of-service attacks of malicious consumers and free riding of peers. Pointing to these problems, a bi-evaluation^*** trust management model, called BiTrust, is proposed. In this model, the trustworthiness of a peer is divided into service and request trustworthiness. Service trustworthiness shows the resources reliability of providers, and request trustworthiness is used to deal with requests from consumers, which can keep away malicious consumers and encourage peers to share resources. A generic method for evaluating service and request trustworthiness is described. Furthermore, the implementation strategies of the model are also depicted in this paper. The following analysis and simulation show that BiTrust is more effective on enhancing high-quality resources sharing among peers and more advanced in successful exchanges rate.

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This paper proposes an adaptive bandwidth control scheme for the private wireless networks. Carrier sense multiple access with collision avoidance (CSMA/CA), which is commonly used within the private networks, is not efficient in terms of spectral efficiency due to its strict collision avoidance process. In order to relax the collision avoidance rule, this paper employs dynamic spectrum control (DSC), in which a certain number of discrete spectra having the higher channel gain is selected in a manner with each link allowing a partial band interference. Such interference may be suppressed by the equalizer at the receiver. Aiming at optimal selection of the bandwidth for the DSC according to channel realizations, in the sense of throughput maximization, this paper proposes a channel capacity maximization-based BAR control scheme. Computer simulations validate that the proposed scheme achieves high throughput efficiency.

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Autonomous ad hoc networks are networks with nodes belonging to different authorities, and cooperative behavior of nodes is not guaranteed in such networks. In this paper, defense mechanisms are introduced to protect nodes against injecting traffic attacks in an autonomous ad hoc network, and to stimulate nodes to forward packets for each other. We have a cross-layer approach in the design of our mechanisms, and nodes use information from medium access control (MAC) layer for selecting a good route. In addition, nodes attempt to drop packets of those nodes that violate MAC layer backoff mechanism. Analytical and simulation results demonstrate the effectiveness of our proposed mechanisms in the presence of injecting traffic attacks and MAC layer misbehaviors in an ad hoc network that consists of nodes.

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Based on stated preference (SP) data collected in Ho Chi Minh City, this paper applied a latent class (LC) - standard ordered response model (SORM) to explore attitude of respondents towards Park-and-Ride (P&R) and Transportation-Eco-Point (TEP) policies. The LC model assigned the respondents into "altruistic" and "" classes. Then, the SORM determined the respondents' attitude for each class. In the model, some latent variables estimated from multiple-indicators multiple-causes (MIMIC) model were also considered. Generally, the people with less knowledge, less appropriateness and less recognition of the effects of the new policy belong to the class. It was revealed that the price of prepaid shopping ticket (PPT) and return ratio of TEP (RRT) play very important roles in the respondents' attitude for both altruistic class. In addition, our results suggest that the RRT of 15% and PPT from 0.3 to 0.4 million VND would satisfy both users and government.

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In wireless sensor networks, the on-off attacker nodes can present good behaviors and then opportunistically and selectively behave badly to compromise the network. Such misbehaving nodes are usually difficult to be spotted by the network system in a short term. To address this issue, in this study, we propose a reputation scheme to mitigate the on-off attack. In addition, a penalty module is properly designed so that the reputation scheme can effectively respond to the on-off misbehaviors and make such nodes quickly detected by the system, hence the minimization of their influence. We confirm the feasibility and effectiveness of the proposed scheme through simulation tests.

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Very often, each individual continues to do something for his/her individual advantage that collectively is damaging to the group as a whole. The conflict is labeled as “social dilemma” or “social trap” by social psychologists. The phenomenon is very common in individualistic cultures (the West), but does the same phenomenon exist in collectivistic cultures which value cooperation and group goals more than individual benefits? The present authors employed a “replenishable ocean resource paradigm” that they developed on a series of studies in Taiwan and found that behaviors were indeed very pervasive in the East. Several significant factors that affected the degree of cooperation and/or competition were also identified: sanction system, personal motivation, interpersonal relation, and the composition of decision making groups. In brief, it was found that the lower the severity of punishment or the less probability of being caught, the more the subjects' behaviors became. Subjects with the motives to maximize “individual gain” and “relative gain” competed more and did not differ from each other, while “joint gain” subjects competed the least. In addition, decisions made by group of three or five people were more than the decisions made by the individual. The present authors and their associates also compared the behaviors of Taiwan and American students in the social dilemma situation directly. It was found that subjects from two cultures did differ on the cooperative behaviors. Taiwan subjects were more competitive than American subjects in general. Both “probability of inspection” and “degree of punishment” had significant effect on the Taiwanese's behaviors, but only “inspection probability known or not” affected American subjects. In respects to Collectivism/Individualism Scale, Taiwan subjects did not score higher than American subjects on total collective measure, but Taiwan subjects scored higher than American subjects on collectivism toward spouses, parents, and relatives, and scored less than American subjects on collectivism toward colleagues/classmates and friends. Therefore, Taiwan subjects interacting with colleagues/classmates or friends were more than American subjects. General discussion on the meaning, application and cross-cultural implication of this series of studies concludes this paper.

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In wireless sensor networks, or WSNs, a malicious node is able to cover itself by switching between good and bad behaviors. Even when running under a reputation mechanism, such a node can still behave maliciously now and then so long as its reputation is within the acceptable level. To address this inconsistent behavior issue, a combined approach of statistic reputation and time series is proposed in this study, in which the negative binomial reputation is applied to rate the nodes' reputation and concept of time series is borrowed to analyze the reputation results. Simulations show that the proposed method can effectively counter inconsistent behavior nodes and thus improves the overall system performance.

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In this paper, we investigate multi-service forwarding in wireless networks (SeWN) with relay nodes (RN). The RN's node-selfishness is characterized from the perspectives of its residual energy and the incentive paid by the source, by which the degree of intrinsic selfishness (DeIS) and the degree of extrinsic selfishness (DeES) are defined. Meanwhile, a framework of the node-selfishness management is conceived to extract the RNs' node-selfishness information (NSI). Based on the RN's NSI, the expected energy cost and expected service profit are determined for analyzing the effect of the RN's node-selfishness on the multi-service forwarding. Moreover, the optimal incentive paid by the source is obtained for minimizing its cost and, at the same time, effectively stimulating the multi-service delivery. Simulation validate our analysis.

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Recently, cooperative spectrum sensing is being studied to greatly improve the sensing performance of cognitive radio networks. To develop an adaptable cooperative sensing algorithm, an important issue is how to properly induce users to participate in spectrum sensing work. In this paper, a new cognitive radio spectrum sharing scheme is developed by employing the trust-based bargaining model. The proposed scheme dynamically adjusts bargaining powers and adaptively shares the available spectrum in real-time online manner. Under widely different and diversified network situations, this approach is so dynamic and flexible that it can adaptively respond to current network conditions. Simulation results demonstrate that the proposed scheme can obtain better network performance and bandwidth efficiency than existing schemes.

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