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1 Introduction Ad hoc networks are a new paradigm of wireless communications for laptops (which we called nodes). In an ad hoc network, there is no fixed infrastructure such as base stations and mobile switching centers. mobile nodes to communicate within each radio coverage of other directly via wireless connections, while those who are distant from each other nodes based on messages before the router. node mobility in an ad hoc network causes frequent changes of network topology. On the tactical military operations are still the most important The use of ad hoc networks today. For example, military units (such as soldiers, tanks, aircraft, or), equipped with wireless communication devices could create an ad hoc network when they travel to form a battlefield. The ad-hoc networks can also be used for law enforcement and emergency rescue operations. As an ad hoc network can be deployed rapidly with relatively low costs, it is an attractive option for commercial uses, such as sensor networks or virtual classrooms. Safety First 1 Goals Security is an important issue for ad hoc networks, security, especially for applications. To ensure an ad-hoc network, we consider the following attributes: availability, confidentiality, integrity, authentication and non-refoulement. Availability ensures the survival of network services despite denial of service attacks. A denial of service may at any level of an ad hoc network can be started. On the physical layer and Media Access Control, an opponent of interference papers dealing with the discomfort of physical channels. At the network level, it could disrupt an opponent of the routing protocol and disconnect the network. At higher altitudes, an opponent could throw the high level services. Such an objective is the Key Management Service, an essential service for all security frameworks. Confidentiality ensures that certain information is disclosed to unauthorized persons. network transmission of sensitive information, such as strategic or tactical military information requires confidentiality. Leaking information to the enemy could have devastating consequences. routing information must remain confidential in some cases because the information could identify the enemy, and find their targets in a battlefield value. ensures the integrity of a message is never transmitted damaged. A message has been because of benign failures, such as radio propagation loss or damage due to malicious attacks on the network. Authentication enables a node to guarantee the identity of communication nodes peer. Without authentication, an adversary could masquerade a node, so that unauthorized access to resources and sensitive information and disrupt the operation of other nodes. Finally, non-repudiation ensures that the origin can not deny a message that the message sent. No release is useful for the detection and isolation of compromised nodes. If a node A is a false message from a node, B non-repudiation can convince B to acknowledge with this message and other nodes, the risk B. There are other security objectives (eg approval), which are relevant for some applications, but we will not pursue these issues in this document. First 2 Challenges The main characteristics of ad hoc networks have both challenges and opportunities in achieving security objectives. Firstly, the use of wireless connections allows ad hoc network vulnerable to attacks by replay link passive listening post impersonation active, and the distortion of the message. Eavesdropping might give access to secret information opponent, respect for confidentiality. Active attacks might allow the adversary to delete messages, to inject erroneous messages, changing messages and an output node, and therefore violates the availability, integrity, authentication and non- repression. Second, nodes, roaming in a hostile environment (like a battlefield) physical protection relatively low, have a substantial likelihood of a compromise. Therefore, we must consider not only attacks outside a network, but also consider attacks inside the network will be launched by compromised nodes. Therefore, achieving high survival, ad hoc networks must have a distributed architecture, without two central institutions. The introduction of a central place in our security solution can lead to a significant vulnerability, that is, if this centralized entity is compromised, then the whole network is compromised. Third, an ad hoc network is dynamic due to frequent changes in both its topology and its members (ie, nodes often join and leave the network). Trust between nodes also changes, for example, if some nodes are detected as a compromise. Unlike other mobile wireless networks, such as mobile IP [21, 48, 34], nodes in an ad hoc network can be dynamically join with administrative sectors. While not a security solution with sufficient static configuration would be. It is desirable that our security mechanisms to adjust on the fly to these changes. Finally, an ad hoc network is composed of hundreds or even thousands of nodes. The security mechanisms must be scalable to handle such a large network. First 3 routing protocol and threats routing protocols for ad hoc networks are still actively looking. There is no single standard routing protocol. Therefore, we want to capture the common security threats and provide guidelines to secure routing protocols. In most routing protocols, routers exchange information about the topology of the network to establish links between nodes. This information could be a target for malicious adversaries who want to reduce the network has become. There are two sources of threats to routing protocols. The first comes from outside attackers. By injecting false routing information, the reproduction of old routing information, or distorting routing information, an attacker could successfully load sharing network or introduce excessive traffic in the network by retransmission and inefficient routing. The second and come to the severe nature of the threats from compromised nodes, advertising false routing information to other nodes can. Identification of erroneous information, it is so difficult just have to be signed routing information of each node does not work, because compromised nodes are able to generate valid signatures with its private key. In defense can protect against such threats the first node routing information the same way they protect data traffic, namely the use of cryptographic systems such as digital signatures. However, this defense against attacks compromised servers is inefficient. Worse yet, as we have explained, we can not overlook the possibility of compromised nodes in an ad hoc network. Detecting compromised nodes by routing information is difficult in an ad hoc network by dynamically changing topology: when finding a piece of routing information is not valid, the compromise by a node, or it would could generate invalid may be due to changes in topology. It is difficult to distinguish the two cases. On the other hand we can use to obtain specific properties of ad hoc networks, secure routing. Note that the handle of routing protocols for ad hoc networks must be overcome routing information to reflect the topology changes dynamically. False routing information generated by compromised nodes could, to some extent, are also outdated information. While there is enough correct many nodes, the routing protocol must be able to find ways to get around these nodes compromised. The ability of routing protocols is usually based on collective redundancies inherent – disjointed, perhaps, the connections between nodes – in ad hoc networks. 2nd Key Management Service We use cryptographic systems, such as digital signatures, to protect the routing information and traffic data. Application of these systems generally requires a centralized management service. We take a public key infrastructure because of its superiority in key distribution and implementation of integrity and of non-refoulement. effective secret key systems used to secure the communications of other node to authenticate each other and after a secret session key shared. In a public key infrastructure, each node has a public / private key pair. The public key can be distributed to other nodes, while the private key must be kept secret for individual nodes. This is a trusted entity called certification authority (CA) [11, 47 and 26] for key management. The CA has a public / private key pair, with its public key is known, each node, and the keys to sign certificates bind public nodes. The trusted CA must be online to reflect the outstanding bonds because the bonds may change over time: a public key can be revoked if the owner node is no longer trusted or leave the network, a node can renew its key pair periodically to reduce the likelihood of a brute force attack on the success of its private key. It is problematic to create a Key Management Service with a single CA in ad hoc networks. Net sales for the security of the entire network, is a vulnerable point in the network: If the CA is unavailable, can not the current node public keys of other nodes or to establish a secure communication with others. If the CA is compromised and leaks its private key to an adversary, the adversary can then sign up incorrect certificate with the private key on each node to issue or revoke a certificate. A standard approach to improve the availability of a service is replication. But a simple replica of the AC is the vulnerable service: Compromise of a single replica, which holds the key to private service, could lead to the collapse of the entire system. To resolve this problem, we distribute the trust to a set of nodes, the share of this node, the responsibility for key management. 3rd Push! Photo: Photo Sharing informal ad hoc networks Like the ubiquitous mobile phone cameras changed the practice of photography. Camera phone pictures are usually taken by an exchange in the soul. Meanwhile, the public online photo sharing is becoming more popular with sites such as Flickr. Push! The photo is a photo sharing for mobile applications where images can be publicly and immediately accessible to anyone nearby. The application also automatically search for files on devices in the vicinity of interesting photos and found relevant. Push! Photo shows how it is possible to share digital photos as easy as photo paper. Shoot! Submit! Discover! Enjoy! A third THE PUSH! PROTOTYPE PHOTO The current prototype of Push! Pictures, photos can be made public, and users can browse their own collections and those of others in the region. For devices are close to each other, they automatically launch every other collections of photos from public research Photographs relevant to a car. These photos are a multi-picture slide show, which is extended as shown in the photos are new. beat you to browse photos of an event in a particular image, the user can click on this image in the slideshow. The application will then download all the pictures from nearby equipment during this event. This way, if a user can find an interesting picture in the slideshow, they can easily find other images of the same event. Deciding What are two photos of the same event, information about who is the opposite and used the time of the shooting. The application uses a discovery service for other devices if they are within the WiFi zone is still demand to know who else (push! Picture) is certain, at a time. As the photo is taken, the image resulting from this information over time and the identity of the photographer. The current prototype is an application running on Pocket PCs with wireless cards and external cameras SD 2 THE third related Earlier work with Push! Music [2 files] music were known as media agents that activate independently replaced if you copy between devices on a wireless ad-hoc. The media are trying to find their agents Path of potential listeners to respond to a user, and how a song is automatically copied to the play list. In this way, users discover new music, while listening passively. Other projects have looked at the photo sharing Mobile. Davis et al. mm2 at the notion of co-presence used to share the decision with which [to simplify 1]. Photos can be automatically entered in a central Web server, where access to share photos downloaded receiver. Kohno Rekimoto and instead decide to GPS information and time stamps, if the images are of the same event or not [4]. It is used to enable users to navigate easily use each other’s picture while standing in a group as a topic of discussion. The system also users drag and drop images between themselves and others. In contrast, Push! Photo sharing is a simple mobile use to simplify common view, and using context and marking automatically find you interesting and relevant photos 4 Conclusions In this paper we have analyzed the security threats facing a network ad-hoc and put the objectives of security policy to achieve. First security applications in sensitive areas to require ad hoc networks, high security, on the other hand, ad hoc networks inherently vulnerable to security issues, attacks. Therefore, security mechanisms for ad hoc networks are indispensable. The nature of ad hoc networks presents both challenges and opportunities of these mechanisms. This document focuses on how to secure routing and how to create a secure key management service in an ad hoc networking. These two questions are fundamental to achieving our security objectives. In addition to standard security mechanisms, we use redundancy in ad hoc network topology and the use of diversity coding on multiple routes tolerate benign and Byzantine faults. To build a highly available and highly secure key management service, we propose to use the first threshold cryptography to distribute trust among a group of servers. In addition, our service offers key management and share original services to ensure proactive security and adapt to changes in the network in a scalable manner. Finally, by relaxing the requirement of consistency on the servers, not the end of our services are based on assumptions synchrony. These assumptions could lead to a security vulnerability. A prototype of the function key management has been implemented, demonstrating its feasibility. This document represents the first step of our research to analyze the security threats in order to understand the security requirements for ad hoc networks and identify existing technologies and propose new mechanisms for securing ad hoc networks. More work must be done to these security mechanisms are in use to investigate ad-hoc network and the impact of these mechanisms on the safety performance of the network. 5 Acknowledgements I want to thank my friends for their valuable contribution to this work. I am also grateful to my family and the anonymous reviewers for their comments and suggestions which have helped improve the quality of the paper. I thank the Almighty for his blessings on me. 6 References [1] E. Ayanoglu, C.-L. I R. D. Gitlin, and J. E. Mazo. Coding for transparent self-healing diversity and communication networks fault tolerant. 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