Wireless Sensor Network consists of spatially distributed autonomous sensors to monitor environmental conditions of the earth. The development of wireless sensor networks was motivated by military applications such as battlefield surveillance. Wireless Sensor Networks (WSN) are deployed at critical places like surveillance, monitoring, airports, battlefield applications hence securing wireless sensor networks is a very challenging task.
Following are the Security Requirements in Wireless Sensor Networks.
Confidentiality requirement is required to ensure that sensitive information is well protected and not revealed to unauthorized third parties.
The confidentiality objective helps to protect information traveling between the sensor nodes of the network or between the sensors and the base station from disclosure, since an adversary having the appropriate equipment may eavesdrop on the communication. By eavesdropping, the adversary could overhear critical information such as sensing data and routing information. Based on the sensitivity of the data stolen, an adversary may cause severe damage since he can use the sensing data for many illegal purposes i.e. sabotage, blackmail. For example, competitors may use the data to produce a better product i.e. safety monitoring sensor application. Furthermore, by stealing routing information the adversary could introduce his own malicious nodes into the network in an attempt to overhear the entire communication.
If we consider eavesdropping to be a network level threat, then a local level threat could be a compromised node that an adversary has in his possession. Compromised nodes are a big threat to confidentiality objective since the adversary could steal critical data stored on nodes such as cryptographic keys that are used to encrypt the communication.
As in conventional systems, authentication techniques verify the identity of the participants in a communication, distinguishing in this way legitimate users from intruders.
In the case of sensor networks, it is essential for each sensor node and base station to have the ability to verify that the data received was really send by a trusted sender and not by an adversary that tricked legitimate nodes into accepting false data. If such a case happens and false data are supplied into the network, then the behavior of the network could not be predicted and most of the times will not outcome as expected.
Authentication objective is essential to be achieved when clustering of nodes is performed. clustering involves grouping nodes based on some attribute such as their location, sensing data etc and that each cluster usually has a cluster head that is the node that joins its cluster with the rest of the sensor network (meaning that the communication among different clusters is performed through the cluster heads). In these cases, where clustering is required, there are two authentication situations which should be investigated; first, it is critical to ensure that the nodes contained in each cluster will exchange data only with the authorized nodes contained and which are trusted by the specified cluster (based on some authentication protocol). Otherwise, if nodes within a cluster receive data from nodes that are not trusted within the current community of nodes and further process it, then the expected data from that cluster will be based on false data and may cause damage. The second authentication situation involves the communication between the cluster heads of each cluster; communication must be established only with cluster heads that can prove their identity. No malicious node should be able to masquerade as a cluster head and communicate with a legitimate cluster head, sending it false data or either compromising exchanged data.
Moving on to the integrity objective, there is the danger that information could be altered when exchanged over insecure networks. Lack of integrity could result in many problems since the consequences of using inaccurate information could be disastrous, for example for the healthcare sector where lives are endangered.
Integrity controls must be implemented to ensure that information will not be altered in any unexpected way. Many sensor applications such as pollution and healthcare monitoring rely on the integrity of the information to function with accurate outcomes; it is unacceptable to measure the magnitude of the pollution caused by chemicals waste and find out later on that the information provided was improperly altered by the factory that was located nearby the monitored lake. Therefore, there is urgent need to make sure that information is traveling from one end to the other without being intercepted and modified in the process.
One of the many attacks launched against sensor networks is the message replay attack where an adversary may capture messages exchanged between nodes and replay them later to cause confusion to the network. Data freshness objective ensures that messages are fresh, meaning that they obey in a message ordering and have not been reused. To achieve freshness, network protocols must be designed in a way to identify duplicate packets and discard them preventing potential mix-up.
5. Secure Management
Management is required in every system that is constituted from multi-components and handles sensitive information. In the case of sensor networks, we need secure management on base station level; since sensor nodes communication ends up at the base station, issues like key distribution to sensor nodes in order to establish encryption and routing information need secure management. Furthermore, clustering requires secure management as well, since each group of nodes may include a large number of nodes that need to be authenticated with each other and exchange data in a secure manner. In addition, clustering in each sensor network can change dynamically and rapidly. Therefore, secure protocols for group management are required for adding and removing members and authenticating data from groups of nodes.
Availability ensures that services and information can be accessed at the time that they are required. In sensor networks, there are many risks that could result in loss of availability such as sensor node capturing and denial of service attacks. Lack of availability may affect the operation of many critical real-time applications like those in the healthcare sector that require a 24/7 operation that could even result in the loss of life. Therefore, it is critical to ensure resilience to attacks targeting the availability of the system and find ways to fill in the gap created by the capturing or disablement of a specific node by assigning its duties to some other nodes in the network.
7. Quality of Service
Quality of Service objective is a big headache to security. And when we are speaking about sensor networks with all the limitations they have, quality of service becomes even more constrained. Security mechanisms must be lightweight so that the overhead caused for example by encryption must be minimized and not affect the performance of the network. Performance and quality in sensor networks involve the timely delivery of data to prevent for example propagation of pollution and the accuracy with which the data reported match what is actually occurring in their environment.
Applications of Wireless Sensor Networks
- Fire detection
- Water quality monitoring
- landslide detection
- Air pollution monitoring
- Data center monitoring