256_4520554_论文格式模板-武汉大学学报英文版-2015, vol.no..doc

409peng hao et al: a mechanism based on reputation in p2p networks to 2015, vol.*no.*, *-*article id doi title：字体arial black，字号小一 author 如：peng *arial 加粗 五号姓前名后，姓全部大写，名首字母大写1, lu *1,2有一个单位以上，在作者名后加上标1,2,若学生为第一作者，导师为通讯作者，则导师名字后加, （姓前名后，姓全部大写，名首字母大写）1. ele作者单位具体到二级单位，给出城市，times new roman 小五号 首行缩进2字符ctronic engineering department, shanghai jiao tong university, shanghai 200240, china;2. school of information security engineering, shanghai jiao tong university, shanghai 200240, china wuhatimes new roman 六号字n university and springer-verlag berlin heidelberg 2011abstract:arial 小五 加粗 in p2p (peer-to-peer) networks, some malicious peers can impact overall networks performance. one of the malicious behaviors of these peers is malicious packet dropping. in this paper, our focus is to detect and to exclude peers that misbehave by dropping some or all packets. here, we propose a reputation-based mechanism for solving the problem efficiently. the proposedtimes new roman 小五 mechanism uses both direct reputation information and indirect reputation information to compute comprehensive reputation of a peer. at the same time, history reputation information is also taken into account when providing in faults tolerance capability and we regulate the imprecision based on the fact that the cause of packet dropping can be complex. finally, the peers with bad comprehensive reputation can be detected easily and then will be excluded from the network. in this way, our proposed mechanism improves the performance of p2p networks without increasing computational overhead.key words: p2p (peer-to-peer); reputation; malicious peers; packet dropping（关键词以分号隔开）clc number: tp 305received datearial 六号 加粗: 2011-06-23times new roman 六号foundation item: supported by the national key basic research program of china(973 program) (2010cb731403) and the opening project of key lab of information network security of ministry of public security (c09607).（注意基金格式） biography: peng hao, male, ph.d. candidate, research direction: network communications and information security. e-mail: penghao2007 作者名后若有，则脚注也应该有，前后呼应to whom correspondence should be addressed. e-mail: 0 introduction一级标题从0开始，实词首字母大写，arial 加粗，四号 （标题每个实词首字母大写）正文内容：字体times new romans，字号五号。公式字号用10.5磅peer-to-peer (p2p)（正文中第一次出现缩写要先写全称后缩写，后文出现用缩写，专有名词首字母大写） networking has become a very active research area in recent years because of its advantages over the traditional client/server model for applications like file sharing, distributed computing, collaborative applications, etc. however, the open nature of p2p networks makes them vulnerable for malicious peers trying to manipulate the network.to solve this problem, many researchers have proposed various methods based on the reputation model and achieved degrees of success. there are mainly three kinds of reputation models: web-based, policy- based, and reputation-based reputation model 1,2（参考文献上标，并需在文中按数字顺序出现）. these models can be directly or indirectly introduced into p2p networks to build reputation between peers. however, while peers identity privacy is important, it is difficult to be achieved in fully distributed p2p networks, because reputation usually depends on information related to identity.previous works have focused on developing various reputation models and enhancing identity privacy for p2p networks in a number of ways. ref. 3（当以ref.*类型出现时不上标） discusses the conflicts between privacy and reputation and proposes a trade-off model between them. in this model, it introduces multi-pseudonym to protect peers identity privacy. although all the pseudonyms of a peer may not be linked together by attackers, privacy is not well protected because each pseudonyms transaction can still be linked. ref. 4 alleviates the identity privacy problem in reputation negotiation by hiding the peers credentials. however, the negotiation process also depends on the disclosure of information related to each peers identity. ref. 5 proposes a reputation-based p2p network to achieve peers anonymity by changing the pseudonym. however, it is implemented using an online trusted third part (ttp).it is acknowledged that identity privacy in fully distributed p2p networks is desirable and necessary, but hard to achieve when building reputation. therefore, in this paper we propose an assessment mechanism for p2p networks based on reputation to alleviate this problem. a reputation model is also developed to improve the safety of p2p networks by implementing a reputation management method. the rest of the paper is structured as follows. section 1 describes the proposed mechanism. section 2 simulates the mechanism and analyzes its performance. finally, section 3 concludes the paper.（引言中简单介绍研究背景，针对某些问题的研究现状，这些前人的研究存在某些不足，引出本文的研究。最后一段简单介绍本文的结构）1 proposed mechanismin our design, the way of preventing malicious packet dropping in p2p networks is the detection and exclusion mechanism. neighbor detecting reputation mechanism has been suggested as a means to reduce the opposite effect of malicious peers. in this section, a reputation-based mechanism will be stated in detail for detecting malicious peers.our mechanism requires the following assumptions to accomplish its functions properly: 1,2,3用带圈数字 all peers can operate in local mode for neighbor detecting. misbehaving peers are considered to be selfish and not malicious. intrusion prevention measures, such as authentication and digital signature, serve as the first line of defense. the network is a multi-forwarding network.1.1 rep数字与标题之间空两格，二级标题arial 五号 加粗，三级标题times new roman 五号（与中文一致，实词首字母大写）utation modelas mentioned above, the properties of p2p networks, such as peer-independence and lack of central management, means that detecting in p2p networks can only be performed in a fully distributed way. thus, each peer should be responsible for detecting its neighbors behaviors for itself. we present a reputation-based assessment mechanism for detecting and excluding malicious peers. the proposed mechanism relies on reputation mechanism for detecting neighbor peers forwarding and for computing whether a peer is malicious or not. here are some related definitions.definition 1类似的定义、算法、定理、公理、引理等都需加粗，且空两格接正文 assessment of direct reputation repr- esents direct experience of detecting to a neighboring peer.definition 2 assessment of indirect reputation re- presents the synthesis resulting by aggregating multiple recommendation opinions about a peer.definition 3 assessment of comprehensive reputation represents the final evaluation to neighboring peers. it can be defined as one peers comprehensive perception of another peer with regard to performing forwarding operation. a peer with a good comprehensive reputation means it behaves very well, while peers with bad comprehensive reputation are malicious.1.2 assessment of direct reputationin p2p networks, only fully distributed detecting techniques can be applied in p2p networks because of the lack of a central management peer. assessment of direct reputation in our mechanism depends on neighbor observations and analysis. each peer overhears its neighboring peers packet forwarding activities and detects any abnormal behaviors independently. the reputation value is hard to quantify because many dynamic factors are involved. if a peer detects a packet dropping of a neighboring peer by overhearing, it cannot determine whether the neighbor is selfish or failed to forward because of congestion or collision. then, an approach based on fuzzy analysis can be used to deal with this problem.in our design, the assessment of direct reputation is not only related to a peers packet-forwarding ratio, but also related to the busy state of peers. considering these, we define a packet forwarding ratio and busy degree to evaluate it. peer “a单字符变量斜体，多字符变量正体” computes packet-forwarding ratio of peer “b” using the following metric:公式居中，10.5磅 (1)in formula (1), （单字符变量斜体，多字符变量一律正体，下标是单字符下标斜体，多字符下标正体） is the number of packets forwarded by peer “b” during a fixed time, is the total number of packets forwarded by peer “b” during a fixed time.peer “a” computes peer “b” busy degree using the following metric: (2)in formula (2), is the number of packets forwarded by peer “b” per unit time, is the maximum number of packets that can be forwarded per unit time.according to the rules above, peer “a” computes peer “b” direct reputation d (a, b) using the following metric: (3)where is a weight of packet-forwarding ratio and 减号和半字线需要分开 is a weight of busy degree. packet-forwarding ratio may be deemed to be more important than busy degree, so packet-forwarding ratio will be given greater weight in the reputation calculations.1.3 assessment of indirect reputationdirect observations may not always be effective because of the weakness described in ref. 6. if a peer makes decisions only based on firsthand information, it is hard to make sure whether all of its neighboring peers are normal or not. using second-hand information can accelerate the detection and subsequent isolation of malicious peers in p2p networks.collaborative detection between peers can be achieved by broadcasting reputation information to the neighboring peers. in our design, when peer “a” receives recommendation reputations of peer “b” from l neighboring peers, peer “a” computes the indirect reputation of peer “b” using the following formula: (4)where 多字符变量正体 is the recommendation reputation value of peer “b” from peer ni and is the comprehensive reputation value of peer ni stored in peer “a”.1.4 assessment of comprehensive reputationin our assessment mechanism, every peer has a table that stores a comprehensive reputation value about its neighbors. peer “a” updates the comprehensive reputation value of peer “b” on the basis of d(a,b) and . peer “a” computes comprehensive reputation of peer “b” using the following formula: (5)where is the weight of the direct reputation and a peer can make bigger to increase the weight of its own observation and then to decrease bad influence caused by false information from misbehaving peers. when , it means the peer does not receive recommendation.reputation value should be updated dynamically because of the dynamic environment in p2p networks. so our design takes into account the peers historical reputation, which helps us calculate a peers comprehensive reputation. in this way, peer “a” can compute the comprehensive reputation of peer “b” using the following formula: (6)the first part describes the comprehensive reputation value of peer b figured in the reputation value table of peer “a” in the past. the second part reflects the peer bs new comprehensive reputation value computed currently based on formula (5). is the weight of the peers past comprehensive reputation value and . if , history reputation value will play an important role and vice-versa.each comprehensive reputation is initialized to 0.5. the lower the comprehensive reputation the peer has, the higher the possibility of misbehavior the peer has. when the comprehensive reputation value of a peer is below a certain threshold, it is broadcasted to all the neighboring peers.2 simulation resultsto evaluate the effectiveness of the proposed assessment mechanism, a software simulator built from scratch is adopted. in our simulation design, we use a mesh topology with 25 000（数字达到3位数以上，每3位空一格，小数亦如是） peers selected randomly. this mesh represents a general topology and it can also be applied to specific p2p networks 7. the simulator relies on a discrete time paradigm and the time step is equal to 225 ms数字和单位之间空格. to perform the simulation analysis, we adopted the following parameter values. for the sake of clarity only 10 minutes of the overall simulation is presented. to obtain a realistic simulation we limited the available bandwidth. according to the application characteristics of p2p networks, the bandwidth is unable to keep a sustained speed of 5.00 mb/s, but rather tends to stabilize around a maximum 2.75 mb/s. the movement of all peers was randomly generated with a maximum speed of 2.5 mb/s and an average pause of 30 s. each simulation runs 500 simulation seconds. the result is shown in fig. 1除figure在句首用全称外，在句中都用缩写。. the vertical axis shows the comprehensive reputation value in different forwarding rate, while the horizontal shows the time.from fig. 1（figure在句中作主语是写成figure 1作其他成分写成fig. 1）, it is found that normal peers can obtain a high reputation value ranging from 0.787 to 0.964 after a while; the comprehensive reputation of a peer that forwards packets with a rate of 80%数字与百分号之间不空格 can reach a reputation value ranging from 0.609 to 0.824. as the forwarding rate decreases, the comprehensive reputation of the malicious peer decreases from the value 0.5 to a value close to 0.011 gradually. the changing of comprehensive reputation is gradual. this is because we take history reputation into consideration and deliberate that faults are tolerant. however, the differences of comprehensive reputation between malicious peer and normal peers are still obvious. in this way, we can decide to select which peers to communicate and isolate the malicious peers.fig. 1 comparison of ctimes new roman 小五号 加粗，首单词首字母大写。图中字体用times new roman 小五号omprehensive reputations of different forwarding rates3 conclusionin this paper, we proposed a reputation-based mechanism to counter malicious packet dropping in p2p networks. it can offer defense against malicious peers and improve the peers quality of service, thus it can ensure p2p networks communication security and robustness. however, the mechanism proposed in the paper only uses a reputation threshold to avoid attackers and then attackers in p2p networks may also adjust adaptively. to enhance our design here, in future work, we will introduce other mechanisms such as anonymity and load balance to optimize the mechanism.references1 bertino e, ferrari e, squicciarini a. reputation-x: a peer- to-peer framework for reputation establishment j. ieee transaction on knowledge and data engineering, 2004, 16(7): 827-842. 2 song s, hwang k, zhou r, et al. reputationed p2p transactions with fuzzy reputation aggregationj. ieee internet computing, 2005, 9(6): 24-34.3 seigneur j m, jensen c d. trading privacy for reputationc/ proc 2nd international conf on reputation management (lncs 2995). oxford: springer-verlag, 2004: 93- 107.4 bradshaw r w, holt j e, seamons k e. concealing complex policies with hidden credentialsc/ proc 11th acm conf on computer and communications security, new york: acm press, 2004: 146-157.5 miranda h, rodrigues l. a framework to provide anonymity in reputation networksc/ proc 3rd annual international conf on mobile and ubiquitous networks: networks and services. san jose: ieee press, 2006: 1-4.6 despotovic z, aberer k. p2p reputation management: probabilistic estimation vs. social networks j. computer networks, 2006, 50(4): 485-500.7 lua e k, crowcroft j , pias m, et al. a survey and comparison of peer-to-peer overlay network mechanisms j. ieee commun. survey and tutorial, 2005, 7(2): 72-93.请参考本刊的参考文献格式：注意标点符号，字母大小写，正斜体，期卷起止页码等信息，会议论文注意出版地，出版商等信息齐全）参考文献标准格式（武汉大学自然科学学报英文版）参考文献中的人名，无论是中国人还是外国人，所有作者姓前名后，姓写全（首字母大写），名字缩写，首字母大写：anderson r;日本、韩国作者发表的外文文献按原格式。注意：文章名后面方括号里面是文献类型标记，期刊是j,书是m,会议文集是c，若原文献是中文，再最后面加(ch).应特别注意字体，字号，黑白体，大小写，正斜体不同的文献类型的格式如下：1文献来自期刊：文献序号 作者名(超过三个作者的，第三个作者以后用et al斜体).文章名（仅仅首单词首字母大写，其余小写）j.期刊名（实词首字母大写,斜体）,年,卷（加粗）(期):起止页.（times new roman 小五号字）例1 bertino e, ferrari e, squicciarini a. reputation-x: a peer-to-peer framework for reputation est