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Data Integrity and Availability in Power System Communication Infrastructures
KTH, School of Electrical Engineering (EES), Communication Networks.
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Society is increasingly dependent on the proper functioning of electric power systems. Today's electric power systems rely heavily on information and networking technology in order to achieve efficient and secure operation. Recent initiatives to upgrade power systems into smart grids target an even tighter integration with information and communication technologies in order to enable the integration of renewable energy sources, local and bulk generation and demand response. Therefore for a proper functioning of smart grids, it is essential that the communication network is secure and reliable both in the face of network failures and in the face of attacks. This thesis contributes to improving the security of power system applications against attacks on the communication infrastructure. The contributions lie in two areas.

The first area is the interaction of network and transport layer protocols with power system application layer security. We consider single and multi-area power system state estimation based on redundant telemetry measurements. The state estimation is a basis for a set of applications used for information support in the control center, and therefore its security is an important concern. For the case of single-area state estimation, we look at the security of measurement aggregation over a wide area communication network. Due to the size and complexity of power systems, it can be prohibitively expensive to introduce cryptographic security in every component of the communication infrastructure. Therefore, we investigate how the application layer logic can be leveraged to optimize the deployment of network, transport and application layer security solutions. We define security metrics that quantify the importance of particular components of the network infrastructure. We provide efficient algorithms to calculate the metrics, and that allow identification of the weakest points in the infrastructure that have to be secured. For the case of multi-area state estimation, we look at the security of data exchange between the control centers of neighboring areas. Although the data exchange is typically cryptographically secure, the communication infrastructure of a control center may get compromised by a targeted trojan that could attack the data before the cryptographic protection is applied or after it is removed. We define multiple attack strategies for which we show that they can significantly disturb the state estimation. We also show a possible way to detect and to mitigate the attack.

The second area is a study of the communication availability at the application layer. Communication availability in power systems has to be achieved in the case of network failures as well as in the case of attacks. Availability is not necessarily achieved by cryptography, since traffic analysis attacks combined with targeted denial-of-service attacks could significantly disturb the communication. Therefore, we study how anonymity networks can be used to improve availability, which comes at the price of increased communication overhead and delay. Because of the way anonymity networks operate, one would expect that availability would be improved with more overhead and delay. We show that surprisingly this is not always the case. Moreover, we show that it is better to overestimate than to underestimate the attacker's capabilities when configuring anonymity networks.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , iii, 36 p.
Series
Trita-EE, ISSN 1653-5146 ; 2013:016
Keyword [en]
Cyber security, power systems, communications, state estimation, distributed
National Category
Communication Systems Telecommunications
Identifiers
URN: urn:nbn:se:kth:diva-122447ISBN: 978-91-7501-772-3 (print)OAI: oai:DiVA.org:kth-122447DiVA: diva2:622429
Presentation
2013-05-30, Hörsal F3, Lindstedtsvägen 26, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20130522

Available from: 2013-05-22 Created: 2013-05-21 Last updated: 2013-05-24Bibliographically approved
List of papers
1. Network-Aware Mitigation of Data Integrity Attacks on Power System State Estimation
Open this publication in new window or tab >>Network-Aware Mitigation of Data Integrity Attacks on Power System State Estimation
2012 (English)In: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 30, no 6, 1108-1118 p.Article in journal (Refereed) Published
Abstract [en]

Critical power system applications like contingency analysis and optimal power flow calculation rely on the power system state estimator. Hence the security of the state estimator is essential for the proper operation of the power system. In the future more applications are expected to rely on it, so that its importance will increase. Based on realistic models of the communication infrastructure used to deliver measurement data from the substations to the state estimator, in this paper we investigate the vulnerability of the power system state estimator to attacks performed against the communication infrastructure. We define security metrics that quantify the importance of individual substations and the cost of attacking individual measurements. We propose approximations of these metrics, that are based on the communication network topology only, and we compare them to the exact metrics. We provide efficient algorithms to calculate the security metrics. We use the metrics to show how various network layer and application layer mitigation strategies, like single and multi-path routing and data authentication, can be used to decrease the vulnerability of the state estimator. We illustrate the efficiency of the algorithms on the IEEE 118 and 300 bus benchmark power systems.

Keyword
SCADA communication, state estimation, cyber-physical security
National Category
Telecommunications
Research subject
SRA - ICT
Identifiers
urn:nbn:se:kth:diva-92610 (URN)10.1109/JSAC.2012.120709 (DOI)000305984500009 ()2-s2.0-84863506343 (Scopus ID)
Projects
EU FP7 VikingACCESS
Funder
EU, FP7, Seventh Framework ProgrammeICT - The Next Generation
Note

QC 20140924

Available from: 2012-04-04 Created: 2012-04-04 Last updated: 2017-12-07Bibliographically approved
2. On the Security of Distributed Power System State Estimation under Targeted Attacks
Open this publication in new window or tab >>On the Security of Distributed Power System State Estimation under Targeted Attacks
2013 (English)In: Proceedings of the 28th Annual ACM Symposium on Applied Computing, 2013, 666-672 p.Conference paper, Published paper (Refereed)
Abstract [en]

State estimation plays an essential role in the monitoring and control of power transmission systems. In modern, highly inter-connected power systems the state estimation should be performed in a distributed fashion and requires information exchange between the control centers of directly connected systems. Motivated by recent reportson trojans targeting industrial control systems, in this paper we investigate how a single compromised control center can affect the outcome of distributed state estimation. We describe five attack strategies, and evaluate their impact on the IEEE 118 benchmark power system. We show that that even if the state estimation converges despite the attack, the estimate can have up to 30% of error, and bad data detection cannot locate theattack. We also show that if powerful enough, the attack can impede the convergence of the state estimation, and thus it can blind the system operators. Our results show that it is important to provide confidentiality for the measurement data in order to prevent the most powerful attacks. Finally, we discuss a possible way to detect and to mitigate these attacks.

Keyword
Cyber security, Power systems, state estimation, distributed
National Category
Communication Systems Computer Systems
Identifiers
urn:nbn:se:kth:diva-122442 (URN)10.1145/2480362.2480490 (DOI)2-s2.0-84877942955 (Scopus ID)978-1-4503-1656-9 (ISBN)
Conference
28th Annual ACM Symposium on Applied Computing (SAC)
Note

QC 20130522

Available from: 2013-05-21 Created: 2013-05-21 Last updated: 2014-09-24Bibliographically approved
3. Traffic Analysis Attacks in Anonymity Networks: Relationship Anonymity-Overhead Trade-off
Open this publication in new window or tab >>Traffic Analysis Attacks in Anonymity Networks: Relationship Anonymity-Overhead Trade-off
2013 (English)Report (Other academic)
Abstract [en]

Mix networks and anonymity networks provide anonymous communication via relaying, which introduces overhead and increases the end-to-end message delivery delay. In practice overhead and delay must often be low, hence it is important to understand how to optimize anonymity for limited overhead and delay. In this work we address this question under passive traffic analysis attacks, whose goal is to learn the traffic matrix. For our study, we use two anonymity networks: MCrowds, an extension of Crowds, which provides unbounded communication delay and Minstrels, which provides bounded communication delay. We derive exact and approximate analytical expressions for the relationship anonymity for these systems. Using MCrowds and Minstrels we show that, contrary to intuition, increased overhead does not always improve anonymity. We investigate the impact of the system's parameters on anonymity, and the sensitivity anonymity to the misestimation of the number of attackers.

Publisher
26 p.
Series
Trita-EE, ISSN 1653-5146 ; 2013:007
Keyword
Relationship anonymity, communication overhead, traffic analysis, Bayesian analysis
National Category
Communication Systems Computer Systems
Identifiers
urn:nbn:se:kth:diva-122444 (URN)
Note

QC 20130522

Available from: 2013-05-21 Created: 2013-05-21 Last updated: 2013-09-09Bibliographically approved

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Citation style
  • apa
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