Mobile ad hoc network is said to be an infrastructure less network and it is dynamic in nature. An infrastructure less network is not having any steady infrastructure for the communication. Each node in that type of network can communicate directly with other nodes in the network and there is no necessity of any centralized network access point. A significant thing about these types of networks is that these networks are not having any routers but the wireless nodes work as a routers and a host. These networks don’t have any static or fixed topology.
Wireless mobile ad hoc network has mobile nodes that use wireless transmission to communicate. In these types of networks the nodes are movable and the motion of nodes might be random or periodical .With node mobility nature of nodes, the nodes contain limited battery power & limited bandwidth. In nonappearance of centralized access point or administrator the source & destination communicate via multiple hops. The MANET is also known as a multi hop wireless network. It is an autonomous collection of mobile nodes or users.
1.2 Weakness
Weakness in security system is also called vulnerability. An ad hoc technique may be vulnerable to illegal access because the system is not verify a user’s identity ahead of allowing data access. Wireless mobile ad hoc network is extra vulnerable than wired network. Some of the vulnerabilities or weaknesses are given below:-
Absence of centralized management: Wireless mobile ad hoc network is not having any centralized check or management server or node. The nonexistence of centralized management makes difficult to discover any type of attacks because it is not easy to monitor and manage the traffic in a extremely dynamic and large scale MANET.
Scalability: With the mobility of nodes, network topology of ad-hoc network altering all the time. That’s why in MANET scalability is a main issue concerning security. Security mechanism must be able of handling a large network as well as minor ones.
Cooperativeness: Routing algorithm for mobile ad hoc networks generally assumes that nodes are cooperative and non-malicious. It results to a malicious attacker which can effortlessly become a main routing agent and disrupt network operation by disobeying the protocol conditions and specifications.
1.3 Security Principles
Security includes a group of investments that are sufficiently funded. In MANET, each and every networking functions such as routing and packet forwarding, are execute by nodes themselves in a self-organizing manner. In favor of these reasons, securing a mobile ad -hoc network is extremely challenging. The goals to check if mobile ad-hoc network is secure or not are as follows:
Availability: Availability refers to assets which are accessible to authorized parties at proper times. Availability applies equally to data and to services. It gives the survivability of network service in spite of denial of service attack. It is also means sharing information so as to make sure consistency among redundant resources. Data replication has been broadly used to improve data availability in distributed systems, and we will apply this method to MANETs. By replicating data on mobile nodes which are not the owners of the original data, data availability can be enhanced because there are several replicas in the network and the possibility of finding one copy of the data is higher.
Confidentiality: Confidentiality makes sure that computer-related possessions are accessed only by authorized parties. It means, only those who should have access to somewhat will actually get that access. To keep confidentiality of some confidential information, we need to carry on them secret from all entities that do not have privilege to access them. Confidentiality is occasionally called secrecy or privacy. MANET uses an unlock medium, so usually all nodes inside the direct transmission range can get the data. One method to maintain information confidential is to encrypt the data, and another procedure is to use directional antennas. It also means that the transmitted data can simply be accessed by the anticipated receivers.
Integrity: Integrity means that resources can be customized only by authorized parties or only in authorized manner. Modification includes writing, deleting and creating, changing status. Integrity assures that a message being passed is never corrupted. The integrity utility can be provided using cryptography hash function along with some type of encryption. When trading with network safety the integrity service is often provided implicitly by the authentication service.
Authentication: Authentication enables a node to make sure the identity of peer node it is communicating with. Authentication is fundamentally guarantee that participants in communication are authenticated and not impersonators. Authenticity is ensured because only the rightful sender can generate a message that will decrypt correctly with the shared key. Authentication is basically a process carried out by two parties in order to recognize one another. Without authentication, an unauthorized node could effortlessly ‘come in’ and use the existing resources within the network. The Problem gets of inferior quality if the unauthorized node be a malicious user. So, it is necessary to have a method for preventing an ‘outsider’ from being element of the network.
Non repudiation: Non repudiation is the property which ensures that sender and receiver of a message cannot disavow that they have ever sent or received such a message .This is useful when we want to discriminate if a node with a few undesired function is compromised or not. It means that parties can confirm the transmission or reception of information with another party, i.e. a party cannot falsely deny having received or sent certain data. By producing a signature used for the message, the entity cannot later on deny the message. In public key cryptography, a node A signs the message by means of its private key. All the other nodes can verify the signed message by using A’s public key, and A is not deny that its signature is attached to the message.
Anonymity: Anonymity means all the information that can be used to recognize owner or present user of node should default be kept private and not be distributed by node itself or the system software. It provides the all probable information that can be used to identify the vendor.
Authorization: This property assigns dissimilar access rights to different types of users. For example a network management can be performed by network administrator only. Authorization is a procedure in which an entity is issued a credential which privileges and permissions it has and cannot falsify by the certificate authority. It is also used to allocate different access rights to different rank of users.
1.4 Attacks
Securing wireless mobile ad-hoc networks is an extremely challenging issue. Knowing possible form of attacks is always the initial step towards developing good security solutions. Safety of communication in MANET is essential for secure transmission of information. Nonappearance of any central co-ordination procedure and shared wireless medium makes MANET too vulnerable to digital/cyber attacks than wired network there are a many of attacks that affect MANET.
External Attack: External attacks are performed by nodes that do not belong to the network. It gives congestion sends false routing information or causes unavailability of services. These kinds of attacks try to cause congestion in the network, denial of services (DoS), and advertising incorrect routing information etc . External attacks check the network from regular communication and producing additional overhead to the network.