International Journal of Engineering Trends and Technology (IJETT) – Volume 31 Number 4- January 2016 Survey on En-Route Filtering Schemes for False Data Injection Attack in CPNS Pooja Shukla#1, A.S Bhattacharya*2 1 ME Student, Department Computer Science and Engineering, RTMNU, Nagpur India 2 Assistant Professor, Department Computer Science and Engineering, RTMNU, Nagpur India Abstract — In Cyber-Physical Network Systems (CPNS), false measure into the controller through compromised sensor nodes, which not only threaten the security of the system, but also consume network resources, can be injected by an adversary. To solve this problem, a number of en-route filtering methods have been designed for cyber physical network systems. However, these methods either lack resilience to the number of compromised nodes or depend on the statically configured routes and node localization, which are not suitable for CPNS. Some of the existing en-route filtering methods for false data injection attack and evaluates the performance of these methods based on their features and efficiency are discussed in this paper. A member of the network and it is authorized to access the resources but uses them in an illegitimate way is an internal attacker. By emitting a high-energy signal to disturb the communication in the network are called as remote attack. By changing routing information and replicating data packets, a passive attacker will just drop or monitor packets in a CPNS. The attackers can make communication failure. Keywords — Cyber-physical networked system, data injection attack, sensor networks, and polynomialbased en-route filtering. I. INTRODUCTION The design of Cyber-Physical Network System (CPNS) integrates computing and communication capabilities with monitoring and control of entities in the physical world. Unlike traditional embedded systems, CPS is natural and engineered physical systems, which are integrated, monitored and controlled by an intelligent computational core. A host of CPNS, including the smart grid, process control systems, and transportation systems, are expected to be developed using advanced computing and communication technologies. For avoiding false data which leads dropping of false data in the routing nodes an efficient method is used called an En-route filtering method. There are many en-route filtering methods such as Statistical en-route filtering (SEF), Dynamic en-route filtering (DEF), Virtual energy-based encryption and keying (VEBEK) which are useful for different network models and different applications. The efficiency differs for various schemes. II. ATTACKS IN CPNS Various types of attacks in CPNS involve a destruction and potential threats in the efficient functioning of the network. An external attacker that aims to harm the network can be a random node which is not part of that network masquerades. ISSN: 2231-5381 Fig 1 Attacks in CPNS Figure 1 shows the categorization of attacks that harms networks communication. In routing attacks [6] attacker can access to routing path information and redirect the path. These may mislead routing paths, acting as black holes that swallow packets and lead to selective forwarding of packets through selected sensors. Attacks on information transit [7] can be broadly divided as interruption, interception, modification and false data injection attack. 1. False data injection attack False data injection attacks have recently been introduced as an important class of cyber attacks against smart grid's wide area measurement and monitoring systems. These attacks aim to compromise the readings of multiple power grid sensors and phasor measurement units in order to mislead the operation and control centers. Recent studies have shown that, if http://www.ijettjournal.org Page 214 International Journal of Engineering Trends and Technology (IJETT) – Volume 31 Number 4- January 2016 an adversary has complete knowledge on the power grid topology and transmission-line admittance values, he can adjust the false data injection attack vector such that the attack remains undetected and successfully passes the residue based bad data detection tests that are commonly used in power system state estimation. However, in this paper, they explain the a realistic false data injection attack is essentially an attack with incomplete information due to the attackers lack of real-time knowledge with respect to various grid parameters and attributes such as the position of circuit breaker switches and transformer tap changers and also because of the attacker's limited physical access to most grid facilities. 2. En-Route Filtering An en-route filtering mechanism’s main objective is to enhance the effectiveness of filtering and improve prevention against node compromise. Both the destination node and intermediate nodes check for the authenticity of the packet and false data is identified as early as possible in an en-route filtering schemes. Hence the number of hops the false data will travel is reduced and energy is conserved. Every intermediate node verifies the MAC computed by the previous node in the routing path and then removes that MAC from the received packet in the first phase of en-route filtering mechanism. It computes a new MAC based on its pair wise key shared with the next node to which it should forward the packet, if the verification test is passed. This new MAC attaches to the packet. Finally, it forwards the report to the next node in the route. Received report Check for required MAC Forward packet No MAC verified? Yes No Drop packet No 2.1 Statistical En-route Filtering (SEF) A global key pool, which is divided into 'n' nonoverlapping groups consisted by SEF [13]. A few keys are randomly chosen from one of the group in global key pool and stored in each node before deployment of the nodes. The same nodal group refers the nodes which have keys from same group in global key pool. Similarly, all nodes are divided into 'n' nodal groups via non-overlapping key groups. Tauthentication, i.e, the legitimate packet should carry T MACs created by T nodes from different groups are performed by the SEF method. MAC with any one of the authentication keys stored are created by all these T nodes. Each sensor which detects an event approves the message by generating a keyed MAC by using one of its stored keys. It will be dropped, if a message has insufficient number of MACs. The node verifies all the MACs carried in the report since it has the knowledge about whole global key pool, when the message is received. At a sink node, false data with incorrect MACs that may pass the enroute filtering will be definitely detected. SEF can efficiently detect false data even when the attacker has compromised a number of nodes and has obtained the security keys, if those keys belongs to a small number of key pool groups are shown by the Simulation results and analysis. SEF can filter out 80 to 90% false data within 10 forwarding hops. 3.2. Dynamic En-Route Filtering (DEF) Scheme A legitimate packet is approved by multiple nodes using their own authentication keys in the Dynamic En-route Filtering (DEF) scheme [14]. Before deployment each node is preloaded with a seed authentication key and secret keys that are randomly chosen from a global key pool. The cluster head broadcasts authentication keys to en-route nodes encrypted with secret keys before sending the packet, that will be used for approval. If they can decrypt them successfully then enroute nodes store the keys. Each en-route node validates the integrity of the packet and drops the false ones. Consequently cluster heads send authentication keys to validate the packet. To spread the authentication keys, DEF method involves the usage of authentication keys and secret keys. MAC is valid? Fig 2. Flow of en-route filtering process Figure 2 shows the framework of an enroute filtering process. Here the en-route node receives the packet from source node or previous en-route node in the routing path. Then it checks the authenticity of the received packet by verifying the MAC attached in it. If verification of MAC is confirmed then the packet is forwarded to next en-route node in the path or else the packet is dropped. ISSN: 2231-5381 2.3. VEBEK: Virtual Energy-Based Encryption and Keying For cyber physical network (CPN) VEBEK [15] is a secure network protocol. It uses one-time dynamic key generated by the source node for one packet, so it reduces the overhead of refreshing keys. Here to provide confidentiality of the data RC4 encryption mechanism is used. The key is generated from Virtual Energy based keying module for encryption. The receiving node must keep track of the energy of the sending node to decode and authenticate a message. It verifies its watch list to confirm that the packet came from a node it is watching when an en-route node http://www.ijettjournal.org Page 215 International Journal of Engineering Trends and Technology (IJETT) – Volume 31 Number 4- January 2016 receives the packet. The packet is forwarded without modification if verification fails. Two operational modes VEBEK-I and VEBEK-II are provided by VEBEK. All nodes watch their neighbors and when a packet is received from a neighboring node, its authenticity and integrity are verified in VEBEK-1 mode. It Can catch the malicious node in one hop itself and hence transmission overhead is minimized. But processing overhead is increased due to the decode/encode that occurs at each hop. Node in the network is organized to watch some of the nodes and it cannot find malicious packets in one hop, in VEBEK-II mode. More energy will be spent for node synchronization and this leads to overhead for the node. 2.4. A Bandwidth-Efficient Cooperative Authentication (BECAN) Scheme High filtering and reliability shows by the BECAN [16] compared to other en-route filtering methods.Cooperative neighbor router (CNR) based authentication is used in this method and hence each node requires a fixed number of neighbors.False injected data can be filtered by BECAN through cooperative authentication of the event report by fixed 'k' neighboring nodes of the source node. To minimize complexity BECAN distributes the authentication of en-route to all sensor nodes in the routing path. To reduce bandwidth utilization, it uses bit compressed authentication technique. BECAN cannot handle selective dropping, false routing information from compromised node etc. 3. Performance analysis of en-route filtering methods Based on false data filtering hops and energy consumption in terms of amount of authentication messages transferred, performance of the en-route filtering schemes are evaluated. SEFs filtering capacity is limited and cannot address impersonating attacks. For creating and verifying MACs, here single shared key is used. To generate packets, misuse of keys may occur. DEF has higher filtering capacity. DEF and SEF are independent of topology changes. It can filter only those unauthorized nodes with no session key. It cannot identify the false data injected from the compromised cluster head or any other sensor nodes. DEF filtering techniques are more attack resilient than static techniques. . A significant drawback is that due to refreshing of keys or redistribution from time to time in the network, the communication overhead is increased. The reasons for key refreshing includes updating keys after revocation, to avoid key from becoming DEFs extra control messages and it leads to old, or due to dynamic changes in the topology of network. SEF is simpler as compared to DEF because of operation complexity and extra overheads. For resource limited sensors, DEF is complicated mainly. BECAN is energy efficient with reduced bandwidth utilization. BECAN can filter false data injection attack but it cannot detect other attacks caused by compromised nodes. Table 1: Performance analysis of different en-route filtering methods Filtering Method Statistical En-Route Filtering scheme Uses Network Features False model Highly 1. data and drops false 1. dense report . Multiple Information CPNs nodes jointly produce event False data Sensor nodes are grouped in to cluster 1. grouped 2. Earlier false data filtering. 3. Each node requires key chain for authentication. Randomly injection distributed Eavesdrops of sensor packets nodes False injection data Randomly Inefficient if the number of compromised node exceeds a threshold value For key dissemination Hill 1. More complicated because of extra control messages. Climbing approach is used. 1. Key based on residual 2. Extra control Messages causes tripling of delay of reports. 1. energy 2. Improves Extra energy is needed for synchronization synchronization 2. Fixed path for data delivery. 1. Cannot problem 1. distributed sensor Bit-compressed authentication 2. nodes Cooperative High reliability http://www.ijettjournal.org detect injected neighborhood based filtering mechanism 3. ISSN: 2231-5381 detecting report False data Dynamic En- injection Route Filtering Selective scheme forwarding BECAN scheme Detects Injection spoofing VEBEK scheme Drawbacks false data by compromised Node. 2. Cannot filter gang false data injection attack. Page 216 International Journal of Engineering Trends and Technology (IJETT) – Volume 31 Number 4- January 2016 REFERENCES [1] D. W. Carman, P. Kruus, and B. Matt, “Constraints and Approaches for Distributed Sensor Network Security,” NAI Labs, Tech. Rep. 00-010, September 2000. [2] F.Akyildiz , Y. 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