Abstract – Wireless sensor networks (WSN) consist of tiny devices. These tiny devices have limited energy, computational power, transmission range and memory. However, wireless sensor networks are deployed mostly in open and unguarded environment. One of the major applications of the sensor networks is in military. So security is the greatest concern to deploy sensor network in such hostile unattended environments, monitoring real world applications. Therefore, secure routing is one of the important aspects for wireless sensor networks. The sensor networks depend upon the sensed data, which may depend upon the application. But the limitations and inherent constraints of the sensor nodes does not support the existing traditional security mechanisms in WSN. Now the present research is mainly concentrated on providing security mechanism in sensor networks. In this context, we analysis security aspects of the sensor networks like requirements, classifications, and type of attacks etc., in this survey paper.
Keywords’ Wireless sensor networks (WSN), Denial of Service (DoS), Media Access Control (MAC), Malicious nodes
Wireless sensor networks (WSN) consist of tiny devices. These tiny devices have limited energy, computational power, transmission range and memory. Wireless Sensor networks (WSN) is an emerging technology and have great potential to be employed in critical situations like battlefields and commercial applications such as building, traffic surveillance, habitat monitoring and smart homes and many more scenarios.
However, wireless sensor networks are deployed mostly in open and unguarded environment. A sensor node is a node in a wireless sensor network that is capable of performing some processing, gathering sensory information and communicating with other connected nodes in the network. One of the major challenges wireless sensor networks face today is security. The majority of sensor nodes are deployed in an unattended and hostile environment with active intelligent opposition that makes the networks vulnerable to a variety of potential attacks, the inherent power and memory limitations of sensor nodes makes conventional security solutions unfeasible and hence security is a crucial issue. The unauthorized attackers monitors, listens to and modifies the data stream in the communication channel. Also they sometimes insert their own nodes (which pretend to be actual node) or compromise the node to hide in the sensor network. So, maintaining the authenticity, integrity and confidentiality of data is a major concern in wireless sensor networks.
Various categories of routing protocols like flat-based, Hierarchical, location-based, Network flow and QoS, Mobility-based, Multipath-based, Heterogeneity-based protocols are used for maintaining and management of WSN. The above mentioned category deals with maintenances and management routing information, making the network to live longer by lowering the energy consumption (energy efficient) and maintain network infrastructure. Although these protocols makes the network live longer by making it energy efficient but they lacks in providing proper security mechanism for Wireless Sensor network. Here is a summarized view of possible attacks and their security solutions. Table 1: Layer based attacks and possible security approaches.
Layer Attacks Security Approach
Physical Layer Jamming and
tampering Use spread-spectrum
Techniques and MAC
Data Link Layer Jamming and
collision Use error correcting
Codes and spread-
Network Layer Packet drop,
and tunnel Authentication
Layer Attacks on
II. LITERATURE REVIEW
These are some of the approaches to make sensor networks secure from attackers and malicious nodes in the networks that will harm the integrity and confidentiality of the transmitted data. But before that, a review of the different types of attacks is necessary. Some of the attacks are as follows:
In these attacks, adversary attracts the traffic to a compromised node. The nature of sensor networks where all the traffic flows towards one base station makes this type of attacks more susceptible.
Fig.1 Sink-hole attack
This attack involves tunnelling of messages over alternative low-latency links to confuse the routing protocol, creating sinkholes etc.
Fig.2 Wormhole attack
Selective forwarding attack:
A single node presents multiple identities, which leads to reduced effectiveness of fault tolerant schemes such as distributed storage and multipath etc.
In this attack, a single node i.e. a malicious node will appear to be a set of nodes and will send incorrect information to a node in the network.
Hackers use wireless sniffer software to steal data, spy on network activity, and gather information to use in attacking the network.
HELLO Flood attack:
In this type of attack an attacker with a high radio transmission range and processing power sends HELLO packets to a number of sensor nodes. The sensors are thus influenced that the adversary is their neighbour. As a result, while sending the information to the base station, the victim nodes try to go through the attacker as they know that it is their neighbour and are ultimately spoofed by the attacker.
Spoofed, altered or replaced routing attack:
The most direct attack against a routing protocol is to target the routing information in the network. An attacker may spoof, alter, or replay routing information to disrupt traffic in the network.
Energy drain attack:
In this attack, the malicious nodes route the information over the longest path due to which large amount of energy gets wasted.
The black hole attack is one of the well-known security threats in wireless mobile ad hoc networks. The intruders utilize the loophole to carry out their malicious behaviours because the route discovery process is necessary and inevitable.
Node replication attack:
An attacker seeks to add a node to an existing sensor network by copying the nodeID of an existing sensor node. A node replicated in this approach can severely disrupt a sensor network’s performance.
Attackers basically send out packets to collide with legitimate ACK packets so that the data sender will need to reschedule the data transmission.
Denial of service attack:
This attack is produced by the unintentional failure of nodes or malicious action. DoS attack is meant not only for the adversary’s attempt to subvert, disrupt, or destroy a network, but also for any event that diminishes a network’s capability to provide a service.
Attacks on information transit:
In case of wireless sensor networks, each node reports changes to a cluster head or base-station only for data above some threshold. Information in transit may be altered, spoofed, replayed again or vanished. In this type of attack attacker has high processing power and large
range of communication.
Routing and data forwarding is a crucial service for enabling communication in sensor networks. Unfortunately, current routing protocols suffer from many security vulnerabilities. For example, an attacker might launch denial-of- service attacks on the routing protocol, preventing communication. The simplest attacks involve injecting malicious routing information into the network, resulting in routing inconsistencies. Simple authentication might guard against injection attacks, but some routing protocols are susceptible to replay by the attacker of legitimate routing messages. Many security approaches are proposed, some of them are key distribution method, spread spectrum, authentication techniques. List of some techniques are:
‘ Unique pair wise keys
‘ Error correcting code
‘ Key management schemes
‘ Random key re-distribution
‘ Radio resource testing
‘ Bidirectional Verification
‘ Multi-path multi-base station routing
‘ Adaptive antennas
‘ Two way authentication
‘ Three way handshake
These techniques works only on some particular attacks and therefore don’t provide that much level of security as desired in maintaining the integrity and confidentiality of data being transmitted over the network. In this report, we proposed a technique called ‘Detection-based path hopping’ for better security in WSN. This is a two-step technique which involves combination of finding the authenticated node and path hopping.
III. DETECTION BASED PATH HOPPING TECHNIQUE
Detection based hopping technique is used to make the wireless network more secure. This technique works in three phases:
Fig.3 Steps of Detection based path hopping
Steps followed in the Detection based path hopping are as follows:
1. At first, we will select number of nodes we want to deploy. To make the WSN more effective, a large number of nodes are required. So, we have to select a large number of nodes.
2. After the deployment of nodes, a sender node called as ‘Master Node’ is considered and declared as authenticated node in that network.
3. In the second phase, detection procedure is followed to identify the authenticated nodes. Master node (MN) sends an authentication detection message to all the nodes in the network. For authentication network key method is used where a single key is distributed all over the network.
4. In response to that message, all the nodes will reply to the master node. In the authentication reply they will send their network id and a Network key to master node.
5. Authenticated and unauthenticated or malicious nodes are then differentiated by making a database containing both types of nodes.
6. The next step after selecting the sender and receiver is data transmission phase. In this phase data transmission will take place between nodes.
7. The sender will first calculate the shortest path to the neighbour in the direction to the receiver. To calculate distance, ‘distance formula’ will be used by the sender.
Distance vector is method to calculate distance between two points in two dimension plane. Let suppose there are two points p1 and p2 having coordinates (x1, y1) and (x2, y2) respectively. The distance formula to calculate the distance between two points’ p1 and p2 will as follows:
Distance (d) = ‘(x2-x1) ??2 – (y2-y1) ^2
Where d is the distance between p1 and p2.
This value of d will decide the next intermediate in the path.
8. After the selection of the shortest path to next node the sender node will check whether the node with shortest path is an authenticated node or malicious node.
9. If the node with shortest path is an authenticated node then the sender will send data to that node otherwise if next node is a malicious node than the sender will check node with less distance and same procedure will be performed until an authenticated node will not be found. As soon as authenticated node will be found the sender will be sending data to that node. This procedure is also called path hopping.
Simulation is the imitation of the operation of a real-world process or system over time. Simulation of this approach will be performed using MATLAB. A proper description of the know-how of the technique is described below:
The following figure shows the deployment of the sensor nodes selected at the first step. In the scenario, the sensor nodes are represented by the blue colour.
Fig.4 Node deployment
After nodes are deployed, now we select sender and receiver node, the sender node will become Master Node and will send request for authentication to each node. All receiver nodes then have to send their IDs etc. to the master node.
In the figure given below, the node at the bottom represents the master node whereas all other nodes are receiver nodes. The lines are giving the impact of the various paths through which the master node is broadcasting the single key over the network in order to check for the authenticated nodes.
Fig.5 Node Detection by Master Node
In fig.6, the distribution of authenticated and malicious nodes on the basis of the earlier responses generated by the nodes, is described clearly. All the malicious nodes are represented in the simulation by colours like red, green, dark blue colours and the authenticated nodes are marked by blue colour.
This differentiation helps in choosing the right and accurate path between the sender and the receiver which consists of authenticated nodes only.
Fig.6 Detection of Malicious Node
In the next figure, the various routes from sender to receiver nodes are described, this process is called ‘path hopping ‘. But these paths are not secure because there contain some malicious nodes also.
Fig.7 Path hopping in the Network
In the next simulation (fig. 8), data transmission is taking place. The sender first selects the node with least distance in the direction of the receiver and if the selected node is malicious node than it will select other node with second least distance from the receiver. Similarly this process will work on all the intermediate nodes until the next receiving node.
Fig.8 Data transmission
Using this path for transferring the sensor’s collected data will prevent the data from the intruders and also maintain its confidentiality from the infected/malicious nodes. As this path-hopping technique already filter the malicious nodes, so the nodes involved are authenticated from sink-hole and worm-hole kind of attacks. Also the Pre-detection approach for path-hopping makes this technique protective from spoofing, altered and replayed attacks. This reduces the packet-loss during transmission and thereby results in increasing the packet-delivery ratio.
The three scenarios considered above are:
‘ one is simulation without error
‘ second is simulation with error
‘ simulation with Detection based path hopping method
The most desired parameters on which we can compare these simulations are:
1. Delay in routing
2. Energy loss
3. Packet loss
Fig. 9 Delay comparison
Although using Detection-based path hopping technique takes more time in routing the nodes because of filteration of malicious nodes, required during detection of path but due to its secure nature, its limitation can be can be ignored off or can be recovered using some other technique etc. in the future.
Figure described below displays the energy loss in the above three situations . Due to the occurrence of errors, data transmmission stopped, so energy loss is also less when there are errors. Therefore, in detection-based path hopping technique, energy loss will be more as compared to earlier WSN security techniques.
Fig.10 Energy Loss
The following figure attempts to show the difference of packet losses in original path hopping and in detection-based path hopping technique. Since all the nodes are safe and there is no scope of any attack by the intruder, so packet delivery ratio is also very high in detection-based path hopping. Hence, packet loss is also less as compared to original path hopping.
Fig.11 Packet loss in Path hopping and Detection based path hopping
Wireless Sensor networks have become promising future to many applications. In the absence of adequate security, deployment of sensor networks is vulnerable to variety of attacks. Sensor node’s limitations and nature of wireless communication poses unique security challenges. Here, we have discussed briefly some most common attacks and the techniques generated to recover them. Along with this, we have described detection-based hopping technique which reduces the outside attacks by selecting only the path containing authenticated nodes, for transmitting any kind of sensor’s data in the WSN. A detailed description of the detection-based path hopping is given above in order to make the sensor networking more successful in the coming years.
Simulation of the WSN with errors, without errors, original path hopping and detection-based path hopping techniques are displayed to explain the advantage of detection based path hopping in WSNs. Results have also shown that how this new routing technique increases the packet-delivery ratio as compared to other techniques. Hence, using this technique makes the network more secure than the other existing path hopping techniques.
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