Wireless Security Network (WSN)

 Submitted by Akash Halder

(BCA Department (Session: 2017-2020))

In recent years Wireless Security Network has become a leading area of research. A Sensor is a device that responds and detects some type of input from both the physical or environmental conditions, such as pressure, heat, light, etc. The output of the sensor is generally an electrical signal that is transmitted to a controller for further processing.

What does Wireless Sensor Network (WSN) mean?

Wireless sensor network (WSN) is a group of structural dispersed and dedicated sensors for monitoring and recording the physical conditions of the environment and organizing the collected data at a central location. WSNs measure environmental conditions like temperature, sound, pollution levels, humidity, wind speed and direction, pressure, etc.

A WSN consists of a few hundreds to thousands of sensor nodes. The sensor node equipment includes a radio transceiver along with an antenna, a microcontroller, an interfacing electronic circuit, and an energy source, usually a battery. The size of the sensor nodes can also range from the size of a shoe box to as small as the size of a grain of dust. As such, their prices also vary from a few pennies to hundreds of dollars depending on the functionality parameters of a sensor like energy consumption, computational speed rate, bandwidth, and memory.

They were initially designed to facilitate military operations but its application has since been extended to health, traffic, and many other consumer and industrial areas.

Applications of Wireless Sensor Network (WSN)

We will be having a future where thousands to millions of small sensors form self-organizing wireless networks. So providing security for these sensor networks is essential. But the task is not easy. There are severe challenges like these sensors will have limited processing power, storage, bandwidth, and energy.

We need to overcome these challenges, because security is very much important. Some applications of it are:

• Emergency response information: sensor networks will collect information about the status of buildings, people, and transportation pathways. Sensor information must be collected and passed on in meaningful, secure ways to emergency response personnel.

• Energy management: Energy distribution can be managed in a more handy way when we begin to use remote sensors. For example, the power load that can be carried on an electrical line depends on ambient temperature and the immediate temperature on the wire. If these were monitored by remote sensors and the remote sensors received information about desired load and current load, it would be possible to distribute load better.

• Battlefield management: Remote sensors can help eliminate some of the confusion associated with combat. They can allow accurate collection of information about current battlefield conditions as well as giving appropriate information to soldiers, weapons, and vehicles in the battlefield.

And so on. There are many more other applications of it.

Constraints of Wireless Sensor Network (WSN)

Due to the harsh working environment, there are some especial particularities and constraints, which are outlined as below.

• Limited in Hardware Resources: Sensor nodes are extremely limited in hardware resources, including energy, computational capability and storage space. Due to higher distances and to more complex signal processing at the receivers to compensate for the attenuation of the signal, the power consumed for Sensor nodes are much higher than in terrestrial radio communication. Sensor nodes are deployed in borders like hill area with severe cold where it is inconvenient to charge or replace the nodes’ battery.

• Unreliable Communication Channel: Military Battle Field acoustic channel is temporally, spatially variable, bandwidth limited and dramatically depends on both transmission range and frequency. The further the communication distance, the lower the bandwidth of acoustic channels, most acoustic systems operate below 30 kHz. The Military Battle Field WSN acoustic channel is significantly affected by low temperature, path loss, noise, multipath effect, and Doppler spread. All these factors cause high bit error and delay variance, which result in packet loss probability and high node failure rate.

• Network Topology: While terrestrial sensor nodes are densely deployed, in Military Battle Field, the deployment is deemed to be sparser, due to the cost involved and to the challenges associated to the deployment itself. The network topology is such that all the nodes are connected to its neighbors and communicated to each other strongly.

• Unsecure Environment and Vulnerability: Sensor nodes are very unsafe due to borderline threats. In many of the cases, the wireless sensor nodes are deployed to monitor hostile objects in borderline battle field. Consequently, these nodes could become highly vulnerable to threats and malicious attacks. In general, Military Battle Field WSNs nodes could be physically damaged to be invalid and are also vulnerable to the borderline weather or human attack.

Hazards to Wireless Sensor Network (WSN)

From the topic discussed above, we can conclude that WSNs are vulnerable to various malicious attacks. Let’s discuss few such attacks.

Active attacks: These attacks attempt to alter or destroy transmitted data in the network. They may intercept or attempt to modify or drop packets which can be executed by malicious attackers. The external attacks carried out by nodes that do not belong to the network, which would be easier to detect and defend. The internal attacks are from insider nodes, and can cause considerable damages. Moreover, some internal attacks may come from compromised nodes which are actually part of the network. Hence, internal attacks are more difficult to detect and may cause more severe damages. Encryption, authentication and trust management are some security mechanisms that can prevent such intrusions.

DoS attacks: DoS is a kind of active attack that attempts to make resources unavailable to the legitimate nodes. The attacker will try to prevent legitimate nodes to access services offered by the network.

Node Compromise Attacks: In some specific fields of applications, battle field sensor nodes may be deployed in unattended and even worse hostile borderline regions. The network may consist of tens or hundreds of nodes deployed in large scales, which means that it is unable to ensure the safety of all nodes. An attacker may capture and crack nodes to read or modify data from memory. And even worse, the compromised nodes may be injected to the network as a legitimate node to monitor or disturb, which can cause more severe damages.

Routing attacks: Routing attacks can cause packets unable to be transferred to the destination node, and even disrupt the operation of the network. These types of attacks are mounted on the routing protocols, such as routing table overflow, routing table poisoning, packet replication, and rushing attacks. Through these malicious behaviors, attackers can attract packets and analyze or even drop packets at its will. Cryptographic techniques are often used to defend routing attacks.

Security Protocols for Wireless Sensor Network (WSN)

Some security protocols have been designed to ensure the security of the Wireless Sensor Networks (WSNs). Let’s discuss about such protocols:

Tesla Protocol: Tesla provides authentication for data broadcasts. They bootstrap the security for both mechanisms with a shared secret key between each node and the base station. However, Tesla is not designed to work in limited computing environment. It has some number of reasons for it to not to work in such environment: Firstly, First, Tesla authenticates the initial packet with a digital signature. Clearly, digital signatures are too expensive to compute on our sensor nodes, since even fitting the code into the memory is a major challenge. Standard TESLA has an overhead of approximately 24 bytes per packet. For networks connecting workstations this is usually not significant. Sensor nodes, however, send very small messages that are 30 around 30 bytes long. It is simply impractical to disclose the TESLA key for the previous intervals with every packet: with 64 bit keys and MAC, the TESLA related part of the packet would constitute over 50% of the packet.

TinySec: TinySec is a link layer security architecture that has been included in the TinyOS version. Its design is based on ease of use and minimal load brought on sensor network. TinySec supports two different security options: encryption with identity authentication and only authentication. In identity authentication encryption, data is encrypted and an identity authentication code (MAC) is added to the package. The identity authentication is a must for each package but encrypting the data is an option that can be decided according to the application. TinySec at the tightest security level where identity authentication encryption is used brings 10% extra load on energy, delay, and band width. However, in cases where only authentication is used, this ratio drops to 3%