A Study On Routing for Secure Adhoc Wireless Network

: An ad hoc mobile network is a collection of dynamic nodes and arbitrarily located in such a manner that the interconnections between nodes are capable of changing on a continual basis. The network topology in such a network may keep changing randomly. To provide secure communication within such network, a routing protocol is used to discover routes between nodes. The primary goal of such an ad hoc network routing protocol is correct and efficient route establishment between a pair of nodes so that messages may be delivered in a timely manner. Route construction should be done with a minimum of overhead and bandwidth consumption. In this paper we are examining issues with implementations and giving a way to solutions. Through proposed work we have eliminated the weaknesses of Ad Hoc wireless network mentioned in Dutta et. al. [5]. Also through proposed work, there is a highest level of secure communication.

about the transmission of each other. The exposed terminal problem refers to the inability of a node which is blocked due to transmission by a nearby transmitting node to another node.
II. Literature review and features of proposed system The security protocol designed for ad hoc wireless network faces various challenges like mobility of nodes, resource constraints, error prone channel state and hidden and exposed terminal problems [14]. Solutions for hidden and exposed terminal problem [7] include medium access collision avoidance [12], medium access collision avoidance for wireless [1], floor acquisition multiple access and dual busy tone multiple access [3]. The destination sequenced distance vector routing protocol [17] is a table driven algorithm based on a classical Bellman-ford routing mechanism. Wireless routing protocol [15], Cluster-Head Gateway switch routing protocol which uses hierarchical network topology [2] and source tree adaptive routing protocol [8] are table driven routing protocol. On demand routing protocol execute the path finding process and exchange routing information only when a path is required by a node to communicate with the destination. Dynamic source routing protocol [11], ad hoc on demand distance vector [18] routing protocol, temporary ordered routing algorithm [16], location added routing [13], associatively based routing [21], signal stability based adaptive routing protocol [4] and flow oriented routing protocol [20] are on demand routing protocols. In hybrid routing protocols, each node maintains the network topology information upto m hops. Core extraction distributed ad hoc routing protocol [19], zone routing protocol [9], zone based hierarchical link state routing protocol [10] are hybrid protocols. Characteristics of an ideal routing protocol for ad hoc wireless networks are given in section 7.2.6 of book [14] Proposed work is the extension of Dutta et. al. [5,6] to provide power aware ad hoc on demand distance vector routing protocol for secure communication.
Its features are given below: (1) It is adaptive to frequent topology changes caused by the mobility of nodes.
(2) It provides minimum connection setup time.
(4) It is loop free and free from stale routes. (5) The number of packet collision is minimum because the communication between nodes is very much limited and communication takes place only when it is required. (6) It always takes optimal routes with respect to time. The convergence is quick if signal is strong. The convergence is slow if signal is weak or when there is no signal. (7) It optimally uses the system resources. (8) It provides quality of service with secure communication.

III. Proposed system for complete solution and its limitations
To proceed ahead, we suppose that the transmission range of a node is k feet (It is normally 30 feet for getting strong signal with mobile nodes in ad hoc wireless network, but variations are there). It means k is the diameter of the circle with node as a center. We are taking this circle as a zone. Since nodes are dynamic, sometimes signal is strong and sometimes it is weak. It also happens that any nodes may lose connections for few milliseconds. Practically we found that signals are strong in more than 98% of chances if distance between two nodes is less than k/2. Signals are strong or weak if distance between two nodes is more than k/2 and less than (k-k/4). There will be weak signal or no signal if node will be in the range of (kk/4) and (k+k/4).
In one zone, there may be more than one number of nodes with its own zone. Within zone, signal strength will be high. On the boundary, it will be poor. A network with n number of nodes can have at most {n*(n-1)/2} number of links. For secure connection nodes have to connect through service set identifier (SSID) and password. Password should be different for each and every node. SSID should have the combination of digits (0-9), alphabets (A-Z; a-z) and special characters. We are distinguishing every wireless network with SSID (known as network group). An ad hoc wireless network can have any number of nodes and any number of network groups. It means one node may have on more than one network group. We avoided such situation because it causes excessive energy drain and consequent reduction of lifetime in battery operated devices.
We study the two cases of Ad Hoc Wireless network. These cases provide higher level programming language. CASE (A) : Nodes are connected but some or all are unknown to each other.
Nodes are unknown to each other. They are secretly connected in a network group through secret netID and password. If N i is sending message to N j , it means Ni and Nj are on the same network group. They may be on different zones but within strong transmission range. Each node will make friend from the neighboring nodes. If they wish to increase the friend list, they can. Note that node will select friendship request only if both are connected by strong signals. There may be some nodes which are in strong transmission range of one or more zones but are not interested in network group. For example, in fig. 2 , N1, N3, N6, N7, N8, N9, N10, N12, N13 and N14 are on the same network group while N2,N4,N5,N11 and N15 are not in this group. Since friends have shared the secret key, rule is that, you will not disclose it to more than f persons. Limitations are there on the number of zones and total number of friends due to limited energy resources, scalability and quality of services. Maximum number of friends and zones will be f and z respectively for a network group. Now they can have the secure communication in their network group. At each node, routing information table or path matrix is initialized. For example see table 1. Any node will have routing information up to zone q only (because of limited power resources of a node). If number of nodes are high then it will have routing information up to neighbors only. This table will get updated after every 2 minutes. If a node wants to send message, then it will update the path matrix through beacons before sending message.
With the help of this table, user can find the shortest path (with respect to time) from one node to another and can send data through that path. Data will automatically get deleted after time to live period.
If all the fields are green in the path from source to destination, then time to live will be the shortest time (t) to reach from source to destination. If some or all the fields are orange in the path from source to destination, then time to live will be the (shortest time (t)+t/2) to reach from source to destination. If any of the fields are red in the path from source to destination, then time to live will be the (2*shortest time (t)+t/2) to reach from source to destination If a node receives three or more independent packets from a node Nr within t1 milliseconds, then this act will considered as malicious behavior. That node will stop entertaining node Nr and consider this node as malicious node.
This method gives no guarantee that packet will be indeed received by destination or not. If packet will get lost due to any reason then destination will not receive this packet and it will be lost permanently. Destination will get to know in next message that something is missing, then it can request for previous message.
The drawback of this type of network group is the new group member. We cannot pass important or secret information over here. CASE (B) : Nodes are connected but known to each other All nodes are known to each other. They have to work on an adhoc wireless network. For security, each node will have unique secret code(SCD).All the nodes have the information about themselves only, even if they are known to each other. If they try to disclose SCD to other, then that node will be attacked by malicious node. Rest nodes get unaffected. They are secretly connected in a network group through secret netID and unique password. This network group has fixed number of nodes. Initial setting of network can be done by flooding a message on the network with time to live(TTL),previous node, time to travel(TTT). Information will get appended in this message in each pass and each node will initialize and update its path matrix with TTT between nodes using above message till TTL expires. Entries in this matrix can be done as (i). Null(-), if source and destination is same; (ii). 0, if there is no strong path between Ni and Nj; (iii).
x, if time required to travel from source to destination is x milliseconds; where is x is any real number. Since we are considering only strong signals and making their entries in the table. This table will get updated after every 2 minutes. If a node wants to send message, then it will update the path matrix/table through beacons before sending message. The entries in the table will be done as follows: (i). Entries of strongly connected will be in green while entries of weakly connected will be in orange and entries of not connected will be in red color. (ii).
Initialization of path matrix is explained in case 1. An example of table after initialization in case 2 will be a table like table1 with orange entries will be zero. We try to update the table at regular time interval and before sending a message. (iii).
We will send message secretly with the method used by Dutta and singh [5,6]. We can easily understand above example (in CASE 1) in view of case 2.
All the examples and simulation work, given in Dutta et. al. [5], will be applicable over here with little modification in simulation parameters given in later section of this paper . We are taking another example in which node is requested for updation of path matrix and shortest way to reach to destination N15. Route establishment in this network group is explained through the following table:  15-8-9-10-1 19 (iv). (v).

V. CONCLUSION AND FUTURE PROSPECTS
In this paper we have examined issues with implementations and given a way to solutions. Through proposed routing protocol we have eliminated the weaknesses of Ad Hoc wireless network like limited energy resources and information disclosure, Jamming etc mentioned in dutta et al [5]. Major threats have minimum or no effect in this system. All security services are applied over here. So there is a highest level of secure communication. Future prospects of this work is to increase the simulation parameters like area, nodes etc and examine individual effect of various factors of with respect to these parameters.