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Privacy Preserving Energy Management

Abstract. The improvement of energy efficiency is an important target on all levels of society. It is best achieved on the basis of locally and temporally fine-grained measurement data for identifying unnecessary use of energy. However, at the same time such fine-grained measurements allow deriving information about the persons using the energy. In this paper we describe our work towards a privacy preserving system for energy management. Our solution follows the privacy by design paradigm and uses attribute-based cryptography and virtualization to increase security.

1 Introduction

The increase of energy efficiency is an important target on all levels of society. According to studies [SZ11] [V. 09], it is best achieved when users receive information about their energy consumption such as how much is consumed, when, by which device, in what form. Furthermore, the effectiveness of this measure is best, when information is given close to the point in time energy is consumed [Fis07]. The smart meters increasingly installed in European homes, reporting consumption with a resolution of 15 minutes, are a first step in this direction.

What is true of the individual energy user is also true for energy managers, responsible for decreasing the energy consumption of their organisation, e.g. a company, an office building or a factory: In this context, the collection of energy consumption measurements is usually embedded in an energy management system (EMS) such as ISO 50001 [fSI11], which provides a continuous improvement process supporting the discovery and realization of energy saving potentials. Consumption measurements are compiled using a wide variety of methods, ranging from manual reading of meters to data loggers automatically providing measurement data collected from buildings equipped with thousands of sensors.

A central parameters in the design of an EMS is the resolution of the measurements, both in space and in time. The low end of the spectrum is the single aggregated consumption number manually collected once per year. The advanced end of the spectrum provides real-time measurement data with a temporal resolution of seconds and spacial resolution down to the individual device, plus additional information e.g. on weather or building and device status. The better the resolution, the more targeted and efficient the energy saving measures. For example, a heating system which is not configured properly and thus working at inappropriate hours can be discovered quickly, just as open fridge doors or lights left on.

The problem addressed in this paper is that an EMS can be abused and turned it into a system that monitors e.g. employees via their energy consumption. In Fig. 1 we depict the power consumption of a computer workplace, which shows that it is easy to derive information about the user's workday.

Fig. 1. Detailed energy monitoring tells much about a user's behavior

Correlating energy logs with other information sources, e.g., the system keeping track of working times of employees, is just a further step. It is problematic that the time an employee spends working at her computer can thus be compared to her “claimed” working time.

We conclude that the high resolution measurements (desirable and necessary for improving energy efficiency) and personal privacy appear to be contradicting requirements. When an EMS based on high-resolution measurements is established in an organization, usually the work council is involved and any objections are addressed. This makes the introduction of the EMS more complicated and eventually may endanger its successful operation.

In this paper we present our work towards an EMS that tries to resolve this apparent contradiction. The solution can be applied to similar use-cases where access rights to privacy-sensitive data streams have to be enforced. We first detail the problem in Chapter 2 and outline background information in Chapter 3. Our approach is discussed in chapters 4 and 5.

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