Certain Investigations on Security Issues in Smart Grid over Wireless Communication

INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY VOLUME 4 ISSUE 2 – APRIL 2015 - ISSN: 2349 - 9303

Certain Investigations on Security Issues in Smart Grid over Wireless Communication S.Fathima1

Dr.S.Karthik2

1

PG Scholar, Department of Computer Science and Engineering SNS College of Technology Coimbatore,

Dean & Professor, Department of Computer Science and Engineering SNS College of Technology Coimbatore,

Abstract— Smart Grid (SG) communication has recently received significant attentions to facilitate intelligent and distributed electric power transmission systems. The advent of the smart grid promises to user in an era that will bring intelligence, efficiency, and optimality to the power grid. Most of these challenges will occur as an Internet-like communications network is super imposed on top of the current power grid using wireless mesh network technologies with the 802.15.4, 802.11 and WiMAX Standards. Each of these will expose the power grid to security threats. Wireless communication offers the benefits of low cost, rapid deployment, shared communication medium, and mobility. It causes many security and privacy challenges. The concept of dynamic secret is applied to design an encryption scheme for smart grid in wireless communication. Between two parties of communication, the previous packets are coded as retransmission sequence, where retransmitted packet is marked as ―1‖ and the other is marked as ―0‖.During the communication, the retransmission sequence is generated at both sides to update the dynamic encryption key. Any missing or misjudging sequence would prevent the adversary from achieving key. A Smart Grid platform is built, employing the ZigBee protocol for wireless communication. The Simulation results show that the retransmission and packet loss in ZigBee communication are inevitable and unpredictable and it is impossible of the adversary to track the updating of dynamic encryption key. Even though the DES scheme can protect the encryption key from attackers, the hackers can obtain the keys some time, due to the block size 64 bits used by DES that makes the adversary (hacker) to hack the data. It introduces vulnerabilities and liner crypt analysis; this can be achieved by using AES scheme. The AES uses 128 bits block size for a single encryption key a data of 256 billion gigabytes can be transmitted thus its provide much more safety to user from hacker and it reduces the end to end delay and increases packet transmission rate.

Index Terms— Analyzing Module (AM), Clonal Rate(CR), Smart Grid(SG), WiMAX, ZIGBEE. ——————————  —————————— 1

INTRODUCTION The Smart Grid (SG) is considered as a desirable infrastructure for energy efficient consumption and transmission, where the buildin information flow, facilitate significant penetration of renewable energy sources into the grid, and empower consumer with tools for optimized energy consumption. Essentially, its aim is to create a more flexible, efficient, and reliable power grid. And at the heart of smart grid infrastructure is the communications network.

Cryptography is a method of storing and transmitting data in a particular form so that only those for whom it is intended can read and process it. Cryptography is closely related to the disciplines of cryptology and cryptanalysis. Cryptography includes techniques such as microdots, merging words with images, and other ways to hide information in storage or transit. Cryptography is most often associated with scrambling plaintext (ordinary text, sometimes referred to as clear text) into cipher text (a process called encryption), then back again (known as decryption). Individuals who practice this field are known as cryptographers. Cryptography plays a significant role in improving the integrity and confidentiality of the data in SG. Symmetric cryptographies, such as DES (Data Encryption Standard), Triple AES (Advanced Encryption Standard), are widely employed in SG to effectively defend against possible threats.

Zigbee is a specification for a suite of high-level communication protocols used to create personal area networks built from small, low-power digital radios. Zigbee is based on an IEEE 802.15 stanadard. Zigbee is a low-cost, low-power, wireless mesh network standard targeted at wide development of long battery life devices in wireless control and monitoring applications. Zigbee devices have low latency, which further reduces average current. Zigbee chips are typically integrated with radios and with microcontrollers that have between 60-256 KB flash memory. Zigbee operates in the industrial

scientific and medical (ISM) radio bands. Data rates vary from 20 kbit/s (868 MHz band) to 250 kbit/s (2.4 GHz band).

1.1 Characteristics of Smart Grid The principal characteristics of the Smart Grid include the following,  Self-healing  Empowers and incorporates the consumer  Tolerates security attacks  Provides enhanced power quality  Accommodates a wide variety of generation options 1.2 Advantages of Smart Grid  The Smart Grid helps determine the life cycle of power generation and transmission equipment, schedule preventive maintenance on time.  The use of robust two-way communication, advanced sensors, and distributed computing technology improves all round efficiency, reliability, and safety of energy transmissions.  It is greatly helpful to the users in remote areas to get in touch through wireless communication.  A modernization of Smart Grid improves the end-use devices and appliances.  It decreased customer discontent, greater personal and economic security, and greater confidence in public governance.

2. RELATED WORK Yichi Zhang et al. proposed that a distributed intrusion detection system for smart grid (SGDIDS) by developing and deploying an intelligent module, the analyzing module (AM), in multiple layers of

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INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY VOLUME 4 ISSUE 2 – APRIL 2015 - ISSN: 2349 - 9303 the smart grid. Multiple AMs is embedded at each level of the smart grid to improve detection and classify malicious data and possible cyber attacks. In this paper it achieves effective analysis of communication traffic and detects the type of attack, its occurrence into the communication system. But the paper not proposed the optimal combination of different classification techniques and different Intrusion Detection System (IDS) for achieving a higher overall accuracy for intrusion detection. Thus, the scheme is subjected to vulnerabilities. AffinityThresholdScalar(ATS), Clonal Rate(CR), Hyper mutation Rate(HR), Stimulation Threshold(ST) were the parameters considered.

Merits  Effective analysis of communication traffic.  It is possible to detect the type of attack, it’s occurrence into the communication system Demerits  The scheme is subjected to vulnerabilities 3. DYNAMIC ENCRYPTION SCHEME FOR SMART GRID IN WIRELESS COMMUNICATION Integrating information network into power system is the key for realizing the vision of smart grid (SG), but also introduces many security problems. Smart grid is a network of computer and infrastructures to monitor and manage energy usage. Wireless communication offers the benefits of low cost, rapid deployment, shared communication medium, and mobility; at the same time, it causes many security and privacy challenges during transmission.

The concept of dynamic secret is applied to design an encryption scheme for smart grid wireless communication. Synchronous data transmission between sender and receiver using OTF (One Time Frame), within the time data transmission and acknowledgement from receiver will be completed, that is treated as OTF. A node which doesn’t produce the ACK within the time can cause packet loss where retransmission of packet/data again is done. During the communication, the retransmission sequence is generated at both sides to update the dynamic encryption key. Any missing or misjudging in retransmission sequence would prevent the adversary from achieving the keys. The retransmission and packet loss in ZigBee communication are inevitable and unpredictable, and it is impossible for the adversary to track the updating of the dynamic encryption key.

3.1 Methodology The dynamic secret based encryption in smart grid is employed for securing wireless communication. The basic idea of dynamic secret is that the legitimate users dynamically generate a shared symmetric secret key utilizing the inevitable transmission errors and other random factors in wireless communication.

3.1.1 Smart Grid The smart grid (SG) is considered as a desirable infrastructure for energy efficient consumption and transmission, where the built-in information networks support two-way energy and information flow, facilitate significant penetration of renewable energy sources into the grid, and empower consumer with tools for optimized energy consumption.

3.1.2 Dynamic Secret: The sender and receiver monitor the error retransmission in link layer to synchronously select a group of frames. These frames are hashed into dynamic secret to encrypt the data.

This part is a brief introduction of dynamic secret as follows, i) Retransmission analysis /OTF set generation: On the link layer’s communication, error retransmission happens unavoidable and randomly at both side of the sender and the

receiver. According to Stop-and-Wait (SW) protocol, the sender transmits a frame and waits for the corresponding acknowledgement before sending a new frame. If a frame is only transmitted once and its acknowledgement frame is received in time, this frame is named as one time frame (OTF). ii) Dynamic secret generation: The number of OTF set ¥ reaches the threshold ((length of RS), the sender and receiver agree on a uniformly random choice of universal-2 hash functions to compress into the dynamic secret.

Then, the set ¥ is reset to empty. iii) Encryption/Decryption: When a new dynamic secret is generated, it will be applied to update the encryption key at both sides of communication. This symmetric encryption key is used to encrypt the data at sender and decrypt the cipher at receiver. To reduce the computation consumption, the XOR function is used for encryption and decryption.

3.1.3 DSE Scheme for SG Wireless Communication: Dynamic secret-based encryption (DSE) scheme is designed to secure the wireless communication between the smart devices and control center.The DSE scheme consists of retransmission sequence generation (RSG), DS generation (DSG), and encrypt/decrypt. i. Retransmission Sequence Generation (RSG): This module is applied to monitor the link layer error retransmission. The communication packets which have been retransmitted are marked as ―1‖ and the nonretransmitted packets are marked as ―0.‖ The pervious packets are coded as 0/1 sequence ¥, named as retransmission sequence (RS).In DSE, RS is applied to replace the OTF set for dynamic secret generation due to the limitation of computation capability and storage resources. ii. Dynamic Secret Generation (DSG): Once ¥ reaches the threshold (length of RS), it would be compressed to a DS in DSG module. Considering the limitation on computation power, the hash functions are recommended in DSG module.

a) Encrypt/Decrypt: The new dynamic secret is applied to update the dynamic encryption key (DEK) by DEK(k) is generated at both sides of communication synchronously. The sender applies it to encrypt the Data, and the receiver applies it to decrypt the Cipher. XOR function, as one of the most light-weight and easy-implementation algorithm, is applied to update the DEK and encrypt/decrypt the data on both sides. If DEK is shorter than the data, DEK(k) is replicated and padded circularly to generate whose length is equal to the raw data or cipher text.

DSE scheme is an appropriate solution for securing SG wireless communication. It can prevent eavesdropping and forging by utilizing the inevitable errors in wireless communication; can reduce the cost on computation and storage by applying the simple algorithms; can self-organize and self-manage.

3.1.4 Attack case in Smart Grid A smart grid platform is constructed to investigate how the attacker intercepts the communication of smart meter and injects bad data into smart meter. a) Smart grid Platform

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INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY VOLUME 4 ISSUE 2 – APRIL 2015 - ISSN: 2349 - 9303 It established with three sides: Smart Terminal (ST), Control Center (CC), and Adversary. IEEE 802.15.4 standard defines the physical and MAC layers of ZigBee, while the ZigBee Alliance defines the network and application layers. Since it is designed as a low cost, low rate, low power and low complexity personal area network. b) Smart terminal Smart meters are applied to monitor a micro power grid including various electronic devices for displaying, storing, and monitoring all relevant system parameters, such as voltages, currents et al. c) Control Center(CC) Several computers are deployed as the CC . On the CC, the ZigBee module is set as normal mode to communicate with ST. d) Adversary On the Adversary, it is set as promiscuous mode to eavesdrop the communication between the ST and CC. e) Smart grid attack cases Most terminal devices in smart grid are connected into intranet, such as smart sensors and intelligent applications. It is believed that the malicious users could not access them without the intranet and Mac address of these devices. The Adversary obtains the address of the smart meter by monitoring their communication and then injects the false data into the meter. The Adversary can capture the packet sent from ST through Zigbee. The address of ZigBee module on Smart Meter and the short address of coordinator on control center the measurement can be decoded from the data part of the packet.

Using the captured address, attacker can access the smart meter and inject false data. f) Analysis To analyze the security of DSE, the difference between the RS on the CC and Adversary should be listed. Then, retransmitted packet ratio (RPR), packet loss ratio (PLR) and length of RS (L_RS) are investigated to guide the design of DSE. The number of packets is transmitted per seconds; the attacker can capture the data without knowing the packet loss. Control center again retransmit the loss of data to the terminal. Then attacker can generate the dynamic secret with the false data and fail to track the DEK without knowledge of retransmission again he could not start it from the beginning. Thus it is difficult for the attacker to brute force crack the RS. If the Adversary tries to crack the RS, the complexity is related to three key factors: the number of retransmitted packets, the lost packets of the Adversary and the length of the RS. 4. PARAMETERS The performance of network were evaluated using the following metrics, 4.1 Retransmitted Packet Ratio(RPR): The complexity of RS is determined by the number of the retransmitted packet. For example, if there is no retransmitted or non-retransmitted packet, the RS is all-zeroes or all-ones; if there is only 1 retransmitted packet, the Adversary can easily crack the RS using brute force. Thus, we need enough retransmitted and nonretransmitted packets to prevent against the brute force cracking. The number of retransmitted packet is determined by two factors: the RPR and the L_RS. 4.2 Packet Loss Ratio It is the ratio of the number of data packets loss occurs when one or more packets of data travelling across a computer network fail to reach their destination.

4.3 Packet Delivery Ratio It is the ratio of the number of data packets successfully received by the CBR destinations to the number of data packets

generated by the CBR sources.

4.4 Average End – to – End Delay It represents the average delay of successfully delivered CBR packets from source to destination node. It includes all possible delays from the CBR sources to destinations.

5. RESULTS AND DISCUSSIONS The evaluation of performance of the Secure Smart Grid (SSG) protocol was evaluated by comparing it with AODV protocol using NS - 2 Simulator. The security mechanism in Smart Grid makes use of data transmission. Here, the analysis is done for security in data transmission. For comparing the security performance of SSG protocol, a dynamic secret based encryption scheme is used for reducing the security issues of data packet during data transmission.

5.1 Performance Analysis for Retransmitted Rate between AODV Vs. SSG In AODV protocol due to packet loss which leads to excessive packet transmission. It is severe when the number of nodes increases.

It is important to reduce retransmission and packet drops. Compared with AODV protocol, the SSG protocol reduces the rate of Retransmission.

Figure 3.2: Performance Analysis for Retransmission Rate between AODV Vs. SSG 5.2 Performance Analysis for Packet Delivery Ratio between AODV Vs. SSG The SSG protocol can increase the packet delivery ratio due to the reduction in security issues and also parallely reduces the packet drops. On average the packet delivery ratio in SSG protocols is improved when compared with the AODV protocol.

Figure 3.3: Performance Analysis for Packet Delivery Ratio between AODV Vs. SSG 5.3 Performance Analysis for Average End – to – End Delay between AODV Vs. SSG The SSG protocol reduces the average end – to – end delay due to a decrease in number of packet drops. The retransmission increases delay due to too many collisions and interferences thus leading to excessive packet drops and also increases the number of

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INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY VOLUME 4 ISSUE 2 – APRIL 2015 - ISSN: 2349 - 9303 retransmissions. Thus, reducing the retransmission of data packets the delay can be decreased.

Figure 3.4: Performance Analysis for Average End – to – End Delay between AODV Vs. SSG 5.4 Performance Analysis for Packet Loss between AODV Vs. SSG The SSG protocol significantly reduces the security issues during the packet transmission. By applying security mechanism to transmission it reduces the congestion and collision. Thus, compared with AODV protocol it’s reduces the number of packet loss during transmission.

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Figure 3.5: Performance Analysis for Packet Loss between AODV Vs. SSG 6. CONCLUSION A dynamic secret-based encryption scheme is designed to secure the wireless communication of SG. The DSE scheme can protect the users against eavesdropping by updating the dynamic encryption key with retransmission sequence in communication, even the attackers know the details of DSE scheme and obtain the encryption key at some time. It is self-contained, that is, it is dynamically generated during the normal communication without additional traffic and control command. The generated simulation results depicts the security issues thus reducing the retransmission of packets due to packet loss and increase the packet delivery ratio and thus decreasing the end – to – end delay. But the performance gets reduced, since the security issues do not properly overcome by Dynamic secret based encryption. The problem is overcome by using Electing trust head which reduces the retransmission rate and increased packet delivery ratio and decreased end to end delay during transmission.

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