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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>The privacy issues for pseudonymised customers in the Smart Grid</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Hartmut Richthammer?</string-name>
          <email>Hartmut.Richthammer@ur.de</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Department Business Information Systems IV - IT Security Management University of Regensburg</institution>
          ,
          <country country="DE">Germany</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>This is a short overview of the privacy issues for customers in the Smart Grid infrastructure. Smart meter and other devices within the Smart Grid produce a lot of privacy sensitive data. With this nd grained data it is possible to make predictions about the daily routine of a household or create a movement pro le of a vehicle. There are techniques to protect the privacy of a person in network-alike structures, e.g. by creating pseudonyms or anonymizing the ow of data. But this protection does not always work in an adequate way, for example if there are quasi identi er, signi cant or linked pattern, it is possible to depseudonymize and de-anonymize a customer. So it is possible to analyse the daily routine of a person as well as creating a movement pro le of his electrical vehicle or getting some informations about his preferences or issues.</p>
      </abstract>
      <kwd-group>
        <kwd>Smart Grid</kwd>
        <kwd>smart meter</kwd>
        <kwd>privacy</kwd>
        <kwd>anonymisation</kwd>
        <kwd>pseudonymisation</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>-</title>
      <p>A consumer, can also appear as an energy producer, as Prosumer. To stabilize
the grid and protect it from overload and under-supply, it is necessary to keep the
consumption and production of energy in an equilibrium. Therefor the Energy
Service Providers (ESPs) and the Smart Meter Gateways (SMGs) of a Prosumer
are directly connected over the Internet. As a result the acquisition of sensor
data to the split second of consumed and produced energy is possible. Also
controlling data can be submitted from the ESP to the Prosumer. So the Smart
Grid initiate a paradigm change from the pure power grid to a combined power
and communication grid.</p>
      <p>
        This results in the following requirements for the security and privacy which
are prescribed by the German BSI [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ]. The Smart Grid has to be prepared to
protect the ESPs against attacks. By changing the paradigm every Prosumer can
? The research leading to these results was supported by \Bavarian State Ministry
of Education, Science and the Arts" as part of the FORSEC research association
(http://www.bayforsec.de/).
be a victim of a distributed o ense against the ESPs. On the other hand, the
privacy of the Prosumer has to be su ciently protected. This is necessary,
because it is possible to reconstruct a detailed behaviour pro le of every Prosumer
depending on his consumption values [
        <xref ref-type="bibr" rid="ref15 ref16">16,15</xref>
        ].
2
      </p>
    </sec>
    <sec id="sec-2">
      <title>The Privacy issue</title>
      <p>
        In the future the Smart Grid will be a signi cant part of our life and everyone
have to participate and interact with this construct. The industry wants to collect
detailed, ne grained meter data of customers consumption. But each way of
life and behaviour is individual. Thus a person or a household share a lot of
information of its way of life with his ne granulated energy consumption trace.
Figure 1 from Newborough and Augood [
        <xref ref-type="bibr" rid="ref17">17</xref>
        ] shows an example how detailed and
privacy unfriendly such a trace can be. For example it is possible to determine
the point in time when the user leaves the house for work and returns [
        <xref ref-type="bibr" rid="ref15">15</xref>
        ], how
often the refrigerator is active and when the household have breakfast (Fig. 1)
or which TV channel is watched [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ].
      </p>
      <p>
        One additional component of the Smart Grid infrastructure will be electric
vehicles because they can be integrated into the infrastructure in a useful way.
The idea of the Vehicle-to-Grid (V2G) concept is to use the batteries of the
vehicles as centrally coordinated, distributed grid resource [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ]. But there is also
a privacy problem. As Stegelmann [
        <xref ref-type="bibr" rid="ref19">19</xref>
        ] shows, a detailed movement pro le can
be created, because the location information of a connected vehicle is needed to
manage vehicle energy ows. And also the location itself where a person parks
his vehicle can reveal sensitive details. For example if it is parked frequently in
front of a church, a mosque, a hospital or a medical center you can assume which
belief or health condition the driver has. Predictions can be made of potential
reachable destinations with the knowledge of the batteries state of charge (SOC)
[
        <xref ref-type="bibr" rid="ref19">19</xref>
        ].
      </p>
      <p>The privacy problem would be solved, if every consumer has the same and
steady behaviour and consumption, so no individual behaviour could be
identied. But this is not a realistic postulation and we have to nd technical solutions,
which protect the privacy on the one hand and provide the necessary data for
the industry, e.g. for billing, on the other hand.</p>
      <p>
        To protect the privacy of the Prosumer, the BSI claims that anonymisation
and pseudonymisation techniques must be used [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ]. Stegelmann et al. [
        <xref ref-type="bibr" rid="ref20">20</xref>
        ]
describes a possible solution with the help of an example (Fig.2) as following. A
Grid Operator (GO) wants to collect ne grained meter data of customers of
a certain geographical area. The SMG from the Prosumer replaces for all
nonbilling relevant transmissions all identifying informations with a pseudonym.
Then the data are rst encrypted from the SMG for the GO and then signed
by the SMG for the Gateway Operator (GWO). The GWO can now verify the
signature, removes it and send the encrypted message to the GO. The GWO
acts as an transportation layer anonymity service and provides assurance for the
GO of the authenticity of the given data.
      </p>
      <p>
        But the protection of the anonymity over a long period of time is not a trivial
request and this problem is not solved yet. Because a anonymized connection
does not always protect the privacy of an user. Other research work has
demonstrated, that the longterm aggregation of partial information from anonymized
users can break the anonymity and reconstruct the user pro le [
        <xref ref-type="bibr" rid="ref1 ref11 ref12 ref3">1,12,11,3</xref>
        ]. One
concrete problem and a possible solution is shown by Stegelmann et al. [
        <xref ref-type="bibr" rid="ref20">20</xref>
        ]. A
customer could be de-anonymized by tra c analysis, for example based on the
frequency or the absence of communication. To avoid this, enforcing information
ow policies and xed connection intervals could be used.
      </p>
      <p>
        Another privacy protecting method is the creation of multiple pseudonyms
of a Prosumer. The pro t for the Prosumer would be that, if one pseudonym
is uncovered, only a small part of the Prosumer data could be assigned to him.
But multiple pseudonyms has also aws. Jawurek [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ] shows examples for possible
attacks in his work. The `linking by behaviour anomaly' and `linking by behaviour
pattern' attack, are shown in Figure 3.
      </p>
      <p>The linking by behaviour anomaly attack can be used to link either an
identity to a consumption trace or more then one consumption traces together. An
anomaly de nes a singular or a series of unusual events. If this anomaly is
reected in the energy consumption and individual linked to the customers
behaviour, an identi cation is possible. As an example the leaving and coming
home times could be such a linking parameter. This events need to be collected
in a high-resolution. But also a low-resolution identifying event could be used to
identify a user. For example, if the inhabitants leave every weekend or stay at
home on speci c work days.</p>
      <p>The linking by behaviour pattern can be used to link di erent pseudonyms
of one person. A customer can have multiple pseudonyms. For example a new
pseudonym is generated, if the supplier is changed. One other situation could be,
that the supplier wants to protect the anonymity of his customer and generates
a pseudonym after a certain time. For example the pseudonym A is used for the
time interval t and the pseudonym B for the time interval t + 1. The bene t
of this would be, that if an identity is de-pseudonymised, only a nite period
of time is compromise. An attacker could now try to nd a signi cant pattern
inside the consumption traces. If this patterns are found in other consumption
traces of the customers pseudonymised identities, the pseudonyms can be linked.
3</p>
    </sec>
    <sec id="sec-3">
      <title>Conclusion</title>
      <p>
        The Smart Grid brings an innovative change for the electricity market and his
participants. But, as discussed, this change go along with risks for the privacy
of every customer. It would be desirable that the Prosumers have the ability to
protect his own privacy but for changing his individual behaviour. So the solution
should be nd on the modality, how the consumption data are processed and
used. Jawurek et al. [
        <xref ref-type="bibr" rid="ref10">10</xref>
        ] gives a survey of di erent privacy technologies for Smart
Grids.
4
      </p>
    </sec>
    <sec id="sec-4">
      <title>Further Steps</title>
      <p>
        The next step will be the analysis of the question, how detailed and ne
granulated consumption data must be collected. One part of this step will be the
investigation of Intrusion Detection Systems (IDSs). IDS are based on the
analysis of ( ne granulated) information ows and IDSs are necessary to protect the
Smart Grid and the Prosumer, because there are a lot of threats [
        <xref ref-type="bibr" rid="ref13 ref14 ref2">13,14,2</xref>
        ] for
example fraud and sabotage. Customer or the organized crime could try to steal
energy from the ESP, a customer could try to steals energy from his neighbour or
fabricate generated energy meter readings. Another scenario could be sabotage
and interference, where an attacker tries to interrupt the energy supply or to
destroy or damage the grid structures.
      </p>
      <p>
        A de nition of an IDS is given by [
        <xref ref-type="bibr" rid="ref18">18</xref>
        ] as a process which monitor events that
occur in a computer system or network. It analyse signs of possible incidents.
To detect above-mentioned threats, one solution for an IDS could be to collect
and analyse consumption and behaviour data, which brings privacy issues. The
question for this solution is, how detailed must this collected and analysed data
be and how is it possible to combine this with privacy protection? Especially the
question, is the longterm privacy protection also adequate ful lled.
      </p>
      <p>
        One possible method could be the anomaly detection which was early
described by Denning [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ]. Therefor a normal behaviour pattern from the user is
established and the system looks for deviations from this behaviour. But this
proceeding is not very privacy friendly and this solution always has the
requirements to provide enough information to detect intruders and ensure the
conservation of evidence. A decentralized intrusion detection concept, which
involves the Prosumer, could provide more privacy. The Prosumer has detailed
information about his own behaviour and would have an advantage in the
detection of anomalies. The decentralization makes the system solid against single
attacks and Single Point of Failure. As side bene t and in an ideal situation
the Prosumer does not have to share any private data. The challenge for such a
localized concept would be to detect also distributed attacks.
      </p>
    </sec>
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