Conflicts in “Ashes for the Wind” Essay

In the short story â€Å"Ashes For the Wind† by Hernando Tellez, the author uses conflicts to develop the theme that sometimes we have to sacrifice our life to fight corruption. Juan, the protagonist, is a tenant who lives a peaceful life in the village with his wife Carmen and a new born baby. He involves in an external conflict when the corrupt government orders his family to move out of their own place. At the beginning of the story, Arevalo visits Juan’s farm house and tells him â€Å"it would be best for you to clear out†. He then recalls his unpleasant encounter of the same man and a policeman in town; they treat him unfairly. With the policeman carrying whip, and others refusing to sell him oil, Juan senses he is in a bad situation. Moreover, Juan’s external conflict causes his internal conflict since he now faces the dilemma of whether they should move out of their own home. He struggles to find an answer because either way they have to sacrifice something. On one hand he doesn’t want to give up his own place and let the authority wins; On the other hand he jeopardizes his family’s life if they don’t move out. A second intimidating visit soon comes. A Police man fires at his place and Arevalo just stands there â€Å"with hanging head†. In the end Juan chooses to stay in the farm with his wife and son, so they all die in a set up fire. Both external and intenal conflicts are resolved here when the authority appears to win but in fact the author sends out a message that people should not be intimidated and should stand up to corruption like Juan and his family do.

Parallel Imaging. Advantages And Disadvantages Of Parallel Imaging Assignment

Parallel Imaging. Advantages And Disadvantages Of Parallel Imaging - Assignment Example Parallel imaging techniques were not commercially available until recently. They are on the verge of being explored in clinical applications. As has been widely cited, fundamentally, their potential clinical application involves either reduction in the acquisition time or improvement in spatial resolution. Improvements in the quality of images can be realized by reducing the single-shot spin echo sequences, and the fast spin-echo’s train length. Recent studies have hinted that parallel imaging is quite attractive for both vascular and cardiac application and proves more valuable as a 3-T body. Recent studies have shown that magnetic resonance imaging (MRI) can be devoted for establishing means of increasing the acquisition speed. It is worth noting, therefore, that impressive gains have been realized in an effort to make MRI more effective in its application. This paper seeks to provide an overview of fundamental parallel imaging concepts while illustrating on potential clinic al applications. In this paper, merits, demerits of parallel imaging, as well as the comparison between SENSE and GRAPPA as parallel imaging technique would be emphasized. ... Moreover, it has an advantage of not being able to alter the contrast behavior of the imaging sequence underneath (Boesiger, 2002). Described as one with the ability to decrease the time required to perform the image sequence, it causes an increase in the resolution provided there is a specific time measured or be able to perform the two (Boesiger, 2002). For instance in cases where a patient experiences acquisition time exceeding his/her breath-hold capacity, The Parallel imaging can help in addressing this issue through reducing the patient acquisition time by factor 2 or even greater Figure 01. (Glockner et al. 2004) Figure 01.  The  Improved visualization of segmental renal arteries in SENSE IMAGES. IN case, the patient was initially short in breath with difficulty in suspending the respiration for a standard acquisition time. The use of Parallel imaging helped reduce acquisition time from 19s to 10 seconds (Glocker et al, 2004). For the Parallel images that are used in spira l scanning and EPI, they have a faster redouts, which often help to reduce the phase error that often result from BO motion or inhomogenity (Griswold, Jakob, 2002). Through this it help mitigate the T2* decay effect. In this case, motion effects, as well as T2 decay can be reduced and can be reduced when RF echo trains apply. Within the image product, such an advantage can lead to reduced susceptibility, motion artifact, as well as in mitigating of the T2/T2* blurring (Hahn eta l. 2003). In this case, Parallel imaging helps in reducing motion artifact, alongside diminishing the venous contamination, in particular for regions in which there happens to be rapid venous return. For instance, in carotid and renal arteries (figure 02) (Glockner et al. 2004) Figure

Business models Essay Example | Topics and Well Written Essays - 750 words - 1

Business models - Essay Example In this essay an attempt has been made to explain this aspect of the business model with the help of different examples. For this purpose, different research articles and publications have been used. While designing or redesigning the business model it is important to keep in consideration several points like the needs of the customers, what activities will fulfil or satisfy those needs, how the activities will be linked, who will perform those activities, how the value be created for different stakeholders, and what revenue models will be integrated. Hence, it can be said that ultimately the business activities and model should be designed in such a way that there is high value creation for all stakeholders along with delivering high financial performance. Stakeholders’ credibility and financial viability tend to bring in or combine both; financial and social constraints while formulating and designing the overall business model. The business model has two broad factors: on the one hand it keeps in consideration the financial factors and characteristics of the organisation including the methods of revenues, the overall structure of cost, the balance sheet, income statement etc, in order to make sure that all these financial factors are associated with the opportunities and limitations associated with the overall activities and actions of management in order to cut down the costs, increase the revenues, improve the balance sheet and income statement etc. However it is important to understand here that the business model is not only formulated for fulfilling the financial objectives and achieving certain financial returns like specific profit level, return on capital, or other financial goals which reflect overall financial viabi lity. So, on the other hand, business model should also keep in consideration the role of different stakeholders in the overall process of opportunity definition,

Critically evaluate the nature of the relationship between Essay

Critically evaluate the nature of the relationship between intellectual property law and competition law, with particular emphasis on the European Union - Essay Example Article 101 and 102 were regulated as a means of achieving this goal.5 Eventually, the main aim of monitoring competition between undertakings is to protect consumer welfare by striving economic activities. IPRs seem to create conflict with the free movement of goods and services based on the provisions of Article 34 and 36 TFEU6. This essay will critically evaluate the relationship between IP law and Competition Law by focusing on EU perspectives. It will review Article 101 and 102 TFEU on IPRs after indicating detailed information about tension between two disciplines as well as their objectives and policies7. Indeed, since intellectual property rights entitle their owners to exclusive rights on the one hand, while competition law aims to preserve markets open on the other, an inherent tension between the two areas of law is a challenge to their implantation8. Among the main aims of the EU is to set a system of competition law. That informs the reason for creating Article 101 and 102, the Merger Regulation, and State Aid rules. It also explains the justification to pursue a central role in the Treaty as the means for maintenance of effective competition within the European Union.9Besides, The Court of Justice has routinely reaffirmed that the implementation of IPRs, in principle, must correspond to the rules of competition (Article 101 and 102), as well as the rules of free movement of goods referred in Article 34-3710. IPRs are protected under national laws of individual EU countries. Thus, the existence of different national laws on intellectual property produces some difficulties in the EU because of its integration of the single market integration.11 Regarding the aim of free movement of goods throughout the EU, Article 34 (TFEU) outlines restrictions on imports.†12 Article 36 states, â€Å"the protection of industrial and commercial property13† can justify a

The business plan of Super Stars sports facility Essay

The business plan of Super Stars sports facility - Essay Example This paper discusses that Super Stars will be a sports organization which will be focused on enhancing and inculcating sports values among the community members in Bradford city in the United Kingdom. Currently, there are very few multi-sports facilities in Bradford and hence the company hopes to fill this gap. The kind of sporting activities that will be trained includes swimming, skiing, skate boarding, athletics, rugby, golfing, gymnastics, football and hockey. The organizations planned keys to success involves putting the customers wants first and working hard towards satisfying them. The organization will also use appropriate marketing facilities for its services, creating a conducive environment for its operations, purchase quality sports equipments and hiring qualified staffs to assist in the management of the activities. The Super Stars sports facility hopes to target people who have the passion for getting physically fit. It will provide all the necessary facilities that are required in order for people to exercise and attain maximum satisfaction. The members will be both adults and the children and it involves both genders. The sports facility will be a member’s only facility. The membership will be divided into a adult membership, students membership and junior membership. The juniors include children between the age of 5 and 14 years. The adults are those above the age of 14. The membership fee for the junior plan will be 40 pounds plus a 240 pounds annual subscription fee. The adults’ membership fee shall be 50 pounds plus an annual subscription fee of 360 pounds. ... However, students will be granted a fee waiver to encourage them to engage in sporting activities which include a 45 pounds membership fee plus a 300 pounds annual subscription fee. At the beginning of its operations, Super Stars sporting organization will use funds from the government and community contributions to finance its operations. The government has advanced 9,000,000 pounds towards the setting up of the facility. It hopes that the community will contribute 2,000,000 pounds. These funds will be used to purchase the necessary equipments, setting up the entire business, hiring trainers, and maintenance of the facility and equipments. The organization hopes to achieve 52, 000 pounds at the end of the first financial year. By the end of five years the facility hopes that the profits will have increased to around 250,000 pounds per year. Vision Statement The vision statement is a description of the picture of the organization in the long term or in the middle term. It is a clear picture of the organization that describes its desired outcome that seeks to energize, inspire, influence, and enables one to have a mental picture of what the organization hopes to attain( shank, 2005,p.75). It represents a framework for an individual’s comprehensive strategic planning and refers to the inspiration of the organization. It involves the articulation of the organizations dreams and hopes. It helps the organization in making a choice between the current and the future courses of action. It puts together the goals and objectives of the organization. In connection to sporting activities, the vision statement is set so as to provide it with a blueprint for success and set a foundation for what the long term goal is (Elitesportleader, 2012, p. 1). An effective vision

Buddhism Essay Example | Topics and Well Written Essays - 750 words - 4

Buddhism - Essay Example It is considered that the religion was founded on teaching of Gautama Buddha (500 B.C.E). The traditional date of the birth of the Buddha is 560 B.C.E. The Buddha is believed to have been born in northeastern India, and was a prince. He followed ascetic way of life and devoted himself to meditations and spiritual development. One day, he meditated near the Ganges River, and came to conclusion that asceticism did not work and did not help a person to achieve spiritual development. He understood that a person should eat a sufficient amount of food to have a good heath, should take enough rest but not too much, and meditate. In 525 B.C.E, the Buddha achieved Enlightenment and began to preach (Lyons and Peters 1985). As with other major world religions, the history of Buddhism has long been characterized by an ongoing tension between attempts to preserve traditional ideals and modes of practice and the need to adapt to changing social and cultural conditions (Lopez 2002). Many developmen ts in Buddhist history, such as the infusion of esoteric rituals, the arising of forms of devotionalism and lay movements, and the assimilation of warrior practices, reflect the impact of widespread yet fundamental social and cultural changes on traditional religious structures. ... In 480 BC was established the first Buddhist Council at Rajagriha in Bihar. At this council, the Vinaya and Sutra texts were standardized. As with most religions, the early years of Buddhism are shrouded in obscurity. But the period between that event and the reemergence of Buddhism into the light of history around 250 B.C.E. is somewhat unclear. Buddhist tradition holds that there was a meeting, or council, held immediately following the Buddha's death (Lopez 2002). The major concern of this meeting was to stabilize the Buddhist scriptures by coming to an agreement as to what were the accepted scriptures as spoken by the Buddha. For a variety of reasons, no such agreement seems to have been reached, although there was some general agreement on the basic message of the Buddha. Leaving the canon, that is to say the total collection of Buddhist scriptures, open in this way was to lead to disagreements later in Buddhist history. The second Buddhist Council at Vaisali marked the first di vision of the Buddhist Order (386 BC). In 244 BC, the third Buddhist Council called by Asoka. This council fixed the canon of Theravadin Buddhism (Lyons and Peters 1985). To other regions of the world, Buddhist tradition was spread with merchants. For instance, Buddhism was introduced to Southeast Asia in C. 200. Since C. 300, Buddhism is a prominent religion in China and begins to penetrate Korea. c. 750 Buddhism officially established in Tibet (beginnings of the Vajrayana school). c. 800 Ch'an and Pure Land Buddhism become dominant schools in China; establishment of Tendai and Shingon schools in Japan. Only, in 1893 World Parliament of Religions

Vehicular Ad Hoc Networks Essay Example for Free

Vehicular Ad Hoc Networks Essay ABSTRACT. Vehicular Ad Hoc Networks is a kind of special wireless ad hoc network, which has the characteristics of high node mobility and fast topology changes. The Vehicular Networks can provide wide variety of services, ranges from safety and crash avoidance to internet access and multimedia applications. Attacking and misusing such network could cause destructive consequences. It is therefore necessary to integrate security requirements into the design of VANETs and defend VANET systems against misbehaviour, in order to ensure correct and smooth operations of the network. In this paper, I propose a security system for VANETs to achieve privacy desired by vehicles and traceability required by law enforcement authorities, in addition to satisfying fundamental security requirements including authentication, nonrepudiation, message integrity, and confidentiality. Moreover, we propose a privacy-preserving defense technique for network authorities to handle misbehaviour in VANET access, considering the challenge that privacy provides avenue for misbehaviour. The proposed system employs an identitybased cryptosystem where certificates are not needed for authentication. I show the fulfilment and feasibility of our system with respect to the security goals and efficiency. 1 INTRODUCTION VEHICULAR ad hoc networks (VANETs) are receiving increasing attentions from academic and deployment efforts from industry, due to the various applications and potential tremendous benefits they offer for future VANET users. Safety information exchange enables life-critical applications, such as the alerting functionality during intersection traversing and lane merging, and thus, plays a key role in VANET applications. Valueadded services can enhance drivers’ traveling experience by providing convenient Internet access, navigation, toll payment services, etc. Other applications are also possible including different warning messages for congestion avoidance, detour notification, road conditions (e.g., slippery), etc., and alarm signals disseminated by emergency vehicles (e.g., ambulance) for road clearance. The attractive features of VANETs inevitably incur higher risks  if such networks do not take security into account prior to deployment. For instance, if the safety messages are modified, discarded, or delayed either intentionally or due to hardware malfunctioning, serious consequences such as injuries and even deaths may occur. This necessitates and urges the development of a functional, reliable, and efficient  security architecture before all other implementation aspects of VANETs.Fundamentally,VANET security design should guarantee authentication, nonrepudiation, integrity, and in some specific application scenarios, confidentiality, to protect the network against attackers. Besides the fundamental security requirements, sensitive information such as identity and location privacy should be reserved from the vehicle owner’s perspective, against unlawful tracing and user profiling, since otherwise it is difficult to attract vehicles to join the network. On the contrary, traceability is required where the identity information need be revealed by law enforcement authorities for liability issues, once accidents or crimes occur. In addition, privilege revocation is required by network authorities (e.g., network administrator) once misbehaviour is detected during network access. It is less difficult to prevent misbehavior of unauthorized users (i.e., outsiders)since legitimate users and roadside units (RSUs) can simply disregard communication requests from outsiders by means of authentication. Nevertheless, misbehaviour of legitimate users of VANETs (i.e., insiders) is more difficult and complex to prevent, the reason being that insiders possess credentials issued by the authority to perform authentication with peer vehicles or RSUs who canbe  easily tricked into trusting the insiders. Consequently, the insiders misbehaviour will have much larger impact on the network and will be the focus of this paper. I proposed system in this paper and many recent proposals on VANET security provide the option of using anonymous credentials in authentication, rendering it even more complex to handle misbehaviour in VANETs, since the user identity is hidden and cannot be linked arbitrarily which curbs the punishment of misbehaving users. Contributions. Given the conflicting goals of privacy and traceability, and the challenges in designing a privacy-preserving defense scheme for VANETs,  i motivated to propose a security system that can effectively and efficiently solve the conflic ts and challenges. Specifically, my main contributions in this paper include: 1. I propose a pseudonym-based scheme to assure vehicle user privacy and traceability. 2. I design a threshold signature-based scheme to achieve nonframeability in tracing law violators. In this scheme, an innocent vehicle cannot be framed by a corrupted law enforcement authority due to rolesplitting mechanism. 3. A novel privacy-preserving defense scheme is proposed leveraging threshold authentication. It guarantees that any additional authentication beyond the threshold will result in the revocation of the misbehaving users. This defense scheme differs from others mainly in that it yields flexibility in the revocation (i.e., not all types of misbehaviour should be punished). Moreover, the dynamic accumulators in the threshold authentication technique facilitates each user to place further restrictions (besides the threshold) on other communicating users, which is an attractive feature to service providers. 4. My design incorporates mechanisms that guarantee authentication, nonrepudiation, message integrity, and confidentiality. 2 RELATED WORK There is a large body of research work related to the security and privacy in VANETs. The most related works are on the design of privacypreserving schemes. Raya and Hubaux [1]investigated the privacy issue by proposing a pseudonym-based approach using anonymous public keys and the public key infrastructure (PKI), where the public key certificate is needed, giving rise to extra communication and storage overhead. The  authors also proposed three credential revocation protocols tailored for VANETs, namely RTPD,RC2RL, and DRP [5], considering that the certificate revocation list (CRL) needs to be distributed across the entire network in a timely manner. All the three protocols seem to work well under conventional public key infrastructure (PKI). However, the authors also proposed to use frequently updated anonymous public keys to fulfillusers requirement on identity and location privacy. If this privacy preserving technique is used in conjunction with RC2RL and DRP, th e CRL produced by the trusted authority will become huge in size, rendering the revocation protocols highly inefficient. A lightweight symmetric-key-based security scheme for balancing  auditability and privacy in VANETs is proposed in [2]. It bears the drawback that peer vehicles authenticate each other via a base station, which is unsuitable for inter vehicle communications. Gamage et al. [6] adopted an identity-based (IDbased) ring signature scheme to achieve signer ambiguity and hence fulfill the privacy requirement in VANET applications. The disadvantage of the ring signature scheme in the context of VANET applications, is the unconditional privacy, resulting in the traceability requirement unattainable. Group signature-based schemes are proposed in [4] where signer privacy is conditional on the group manager. As a result, all these schemes have the problem of identity escrow, as a group manager who possesses the group master key can arbitrarily reveal the identity of any group member. In addition, due to the limitation of group formation in VANETs (e.g., too few cars in the vicinity to establis h the group), the group-based schemes [4]may not be applied appropriately. The election of group leader will sometimes encounter difficulties since a trusted entity cannot be found amongst peer vehicles. There are also a number of defense techniques against misbehaviour in VANET literature besides those in [1]. An indirect approach via the aid of infrastructure is used in [4].The TA distributes the CRL to the infrastructure points which then take over the TA’s responsibility to execute the revocation protocol. The advantage of this approach is that vehicles never need to download the entire RL. Unfortunately, the conditional anonymity claimed in [4]. only applies to amongst peer vehicles, under the assumption that the infrastructure points are trusted. The infrastructure points can reveal the identity of any vehicle at any time even if the vehicle is honest. Recently, Tsang et al. [7]proposed a blacklistable anonymous credential system for blocking misbehavior without the trusted third party (TTP).The blacklisting technique can be applied to VANETs as: if the vehicle fails to prove that it is not on the blacklist of the current  authenticator, the authenticator will ignore the messages or requests sent by this vehicle. Although not proposed specifically for VANETs, the proposal in [7] has a similar claim as the capability of a TTP (network authority in this paper) to recover a user’s identity in any case is too strong a punishment and highly undesirable in some scenarios. The downside of this  technique is the lack of options to trace misbehaving users, since any user in the system(misbehaving or not)will by no means be identified by any entity including the authorities. I proposed a privacy-preserving defense scheme against misbehavior in [8] leveraging threshold authentication technique. This scheme and the scheme in [3] both preserve user privacy, and simultaneously provide trace ability (i.e., tracing law violators by enforcement authorities in [3] and tracing misbehaving users by network authorities in [8]). The major differences between these schemes are the different technical realizations of the privacy and traceability schemes, due to the different application 3 SYSTEM MODEL We describe the functionalities of our security system and define security requirements in this section. 3.1 Overview Major entities in a VANET environment are depicted in A VANET system diagram. As mentioned before, traceability is needed by law enforcement authorities (LEAs) who require the identity of a violating vehicle to be disclosed for investigating the cause of accidents or crimes. Due to the seriousness of liability issues, if a single authority (e.g., the police) is fully capable of revealing the vehicle identity, this privilege may be abused. It is desirable if two or more authorities (e.g., the police, judge, special agents, and other possible law enforcement authorities) are granted distributed control over the identity retrieval process. One benefit in doing so is that corrupted authorities (the number being less than the threshold) cannot arbitrarily trace vehicle users to compromise their privacy. Another benefit is that malicious authorities cannot falsely accuse (or frame) honest users. Such role-splitting is not required for network authorities since the threshold authentication technique in our defense scheme prevents a network authority from falsely accu sing honest users. The proposed security system primarily consists of techniques addressing the privacy, traceability, nonframeability, and revocation (only by network authorities) issues. The  logic diagram of the entities interactions is depicted in logic diagram, where the arrowed lines indicate the direction of packet flow or physical communications, the bracketed numbers near each line index the major events or procedures between the connected entities. The vehicle users are split into access group owners and members, whereas the RSUs can only be access  group owners. The entities and events/procedures are described in what follows. 3.2 Entities and Procedures The entities in this system are the regional transportation authorities (RTAs), law enforcement authorities (LEAs),network authorities, roadside infrastructure including border RSUs for pseudonym management and regular RSUs (simply RSUs) for Internet access, and vehicle users. Considering practical scenarios, the RSUs in this system are mainly responsible for providing infrastructure access and network services. The RSUs are assumed to be operated by third-party service providers (SPs) who have business contracts with the RTA to build access infrastructure in the RTA’s region. The RSUs are thus not owned by the RTA and have no preestablished trust relationship with the RTA. On the other hand, borders RSUs are owned and operated by the RTA, and can be considered as the agents who are delegated with the RTA’s authority. These entities are involved in the following procedure:  may be caused by malfunctioning hardware and thus is incidental. These types of misbehavior share a common feature, i.e., their occurrence or frequency is low, specifically, lower than a predetermined threshold. Threshold authentication-based defense further consists of six sub-procedures: Membership registration: RSUs and vehicle users register with the RTA to use VANETs. Upon successful registration, a member public/private key pair (mpk;msk) is issued to each RSU and vehicles. The RTA associates the member’s credential with the issued public key and includes this pair of information into a credential list IDlist. Access group setup: RSUs and vehicles setup their own access groups, the member of which is granted privilege to communicate with the access group owner. The group owner adds members to the group and updates related public information. Each added member obtains an access key mak for the group. Access group revoking: The access group owner revokes the granted privilege when deciding to stop communications with a member, due to some decision criteria for misbehaviour. The access group owner removes the member from the access group and updates related public information. Threshold authentication: This procedure is executed between an RSU and a vehicle, or between peer vehicles. We call the authenticator in this procedure Alice who announces the threshold k possibly different for each user being authenticated. The  authentication succeeds if and only if the following conditions are met simultaneously: the user Bob authenticating with Alice is a registered member of the VANET system, Bob is a legitimate member of Alice’s access group (if Alice is an access group owner) whose member privilege has not been revoked, and the authentication threshold has not been exceeded. Alice records the authentication transcripts in AUTHlog: Tracing: This procedure is used by Alice to trace a misbehaving member Mn who attempts to authenticate more than k times. Alice relies on the AUTHlog and public information, and obtains Mn’s credential n as the procedure output which is reported to the RTA.Revocation/recovery: Upon receiving the complaints from other entities in the system as the output of Tracing, the RTA decides if the misbehaving member’s credential needs to be revoked. The RTA then performs the identity recovery by looking up the same pseudonym lookup table PLT (cf.System setup above) which also records the correspondence between the credential n and identity IDn. Note that for the ease of presentation, we assume the RTAs to act as network authorities for the defense scheme in this paper. In reality, when the roles of RTA and network authority System setup: This procedure is executed by the RTA for initial VANET system setup including domain parameter publication, public/private key assignment for entities in the system to perform desired tasks, and database creation for storing necessary records (i.e., the pseudonym lookup table PLT). Pseudonym generation and authentication for privacy: RTA and border RSUs execute this procedure to assign pseudonym/private key pairs to both vehicles traveling in their home domain and vehicles from other RTAs’ domains, so that these vehicles are able to authenticate with RSUs and other vehicles to obtain services and useful messages. Threshold signature for nonframeability: This procedure is invoked by LEAs to share the secret information for recovering a guilty vehicle’s identity. Meanwhile, it prevents corrupted authorities from gathering full power to accuse an innocent vehicle. The functional component of this procedure is the threshold signature. Threshold-authentication-based defense: Designed for the network authorities, this procedure is used to revoke a misbehaving vehicle’s credential, refraining the vehicle from further disrupting system operations. As the core of this procedure, the threshold authentication  technique provides a mechanism to allow certain types of misbehavior that should not result in revocation. For instance, the misbehavior  are separate, the network authority can simply take charge as the RTA in the above sub procedures. Nonetheless, in the execution of Revocation/recovery, the network authority needs to establish trust with or be delegated by the RTA in order to access the PLT. When we mention network authorities in what follows, we implicitly refer to RTAs in the network authority role. 3.3 Security Requirements I define the security requirements for a VANET security system, and will show the fulfillment of these requirements after presenting the design details. 1. Privacy: The privacy requirement states that private information such as vehicle owner’s identity and location privacy is preserved against unlawful tracing and user profiling. 2. Traceability: It is required where the identity information of violators need be revealed by law enforcement authorities for liability purposes. The traceability requirement also indicates that a misbehaving user will be identified and the corresponding credential revoked, if necessary, by network authorities, to prevent this user from further disrupting system operations. Certain criteria have to be met for the traceability of a misbehaving user as explained in the next section. 3. Nonframeability: Nonframeability requires that no entity in the system can accuse an honest user for having violated the law or misbehaved. 4. Other requirements: A secure VANET system should satisfy several fundamental requirements, namely, authentication, nonrepudiation, message integrity, and confidentiality where sensitive information is being exchanged, to protect the system against unauthorized-message injection, denial of message disseminations, message alteration, and eavesdropping, respectively. Nonrepudiation also requires that violators or misbehaving users cannot deny the fact that they have violated the law or misbehaved. 4 CONCLUSIONS AND FUTURE WORK I have presented the VANET security system mainly achieving privacy, traceability, nonframeability, and privacy-preserving defense against misbehaviour and reducing traffic in the network. These functionalities are realized by the  pseudonym-based technique, the threshold signature, and the threshold authentication bas ed defense scheme. The ID-based cryptosystem facilitates  us to design communication and storage efficient schemes. Our future work consists of simulating the proposed security system and experimenting it in real VANET settings. REFERENCES [1] M. Raya and J-P. Hubaux, â€Å"Securing Vehicular Ad Hoc Networks,† J. Computer Security, special issue on security of ad hoc and sensor networks, vol. 15, no. 1, pp. 39-68, 2007. [2] J.Y. Choi, M. Jakobsson, and S. Wetzel, â€Å"Balancing Auditability and Privacy in Vehicular Networks,† Proc. First ACM Int’l WorkshopQoS and Security for Wireless and Mobile Networks (Q2SWinet ’05), pp. 79-87, Oct. 2005. [3] J. Sun, C. Zhang, and Y. Fang, â€Å"An Id-Based Framework Achieving Privacy and Non-Repudiation in Vehicular Ad Hoc Networks,† Proc. IEEE Military Comm. Conf., pp. 1-7, Oct. 2007. [4] X. Lin, X. Sun, P.-H. Ho, and X. Shen, â€Å"GSIS: A Secure and Privacy-Preserving Protocol for Vehicular Communications,†IEEE Trans. Vehicular Technology, vol. 56, no. 6, pp. 3442-3456, Nov. 2007. [5] M. Raya, P. apadimitratos, I. Aad, D. Jungels, and J.-P. Hubaux,â€Å"Eviction of Misbehaving and Faulty Nodes in Vehicular Networks,† IEEE J. Sele cted Areas Comm., vol. 25, no. 8, pp. 15571568,Oct. 2007. [6] C. Gamage, B. Gras, B. Crispo, and A.S. Tanenbaum, â€Å"An Identity Based Ring Signature Scheme with Enhanced Privacy,† Proc.Second Int’l Conf. Security and Privacy in Comm. Networks (SecureComm ’06), Aug. 2006. [7] P. Tsang, M.H. Au, A. Kapadia, and S.W. Smith, â€Å"Blacklistable Anonymous Credentials: Blocking Misbehaving Users without TTPs,† Proc. ACM Conf. Computer and Comm. Security (CCS),pp. 72-81, 2007. [8] J. Sun and Y. Fang, â€Å"A Defense Technique against Misbehavior in VANETs Based on Threshold Authentication,† Proc. IEEE Military Comm. Conf., Nov. 2008.