Unfortunately, privacy is such a complex issue that there is no single solution, no recipe for success, no silver bullet (or set of silver bullets) that will x a system for us so that it is “privacy-safe.” What exactly does it mean anyway, for a system to be privacy-safe? Whose privacy does it protect, when, and to what extent? None of these questions can be answered in general. Instead of a simple one-size-ts-all recipe, one needs to look into each single system Data Types 125 Collection Motivations 126 Data Accessibility 127

3.3.2 e Basics: Privacy Enhancing Technologies 128 3.3.3 Example: Protecting Smart Spaces 131 3.3.4 Example: Protecting RFID Tags 134 Communication Condentiality and Anticollision Protocols 138 Access Control/Tag Deactivation 140 Proxies 142

3.3.5 Example: Protecting Location Information 145 Conclusions 149 Further Reading 150

3.4 How to Address Privacy in Your Ubicomp Work 151 3.4.1 Understand Your Application (Consider Users and Use) 151 3.4.2 Dene the Problem (ink Attacker Model in Security) 152 3.4.3 Know Your Tools (Get the Technical Details Right) 154 Conclusions 155 Further Reading 155

Bibliography 156

and application in great detail, rst understanding what the system does and what the implications of this are, and then working out how (and why) this needs to be changed in order to reach the right behavior.