# Contact Tracing: Ensuring Privacy and Security
## 3 Background Discussion
However, outside of the European Union, proposals exist that expand, rather than limit, the amount of data collected, to increase effectiveness. It is recommended to build a voluntary system that fits the needs set forth by public health authorities. Additionally, it allows a user to enable or disable additional sensors or contextual information they want to use within the application [24]. These recommendations place a lot of trust and responsibility in the hands of the user. In other words, let the user decide how much data they want to share! The idea to add contextual information in contact tracing applications begs the question of what this would do to privacy and security. The use of contextual information in South Korea is examined and it was found that people could be the subject of \"Stereotyping, stigmatisation and discrimination\" [25]. It is for that, and other reasons that the GDPR calls for data minimisation and requires that actors take proportionality (is the expected gain worth it versus the level of breach? ), subsidiarity (can the effect be reached by another, less intrusive method? ), and necessity (is the breach necessary?) into account. From that perspective, enriching data is not a good idea since people could feel compelled or pressured to release more data than they prefer. In addition, if people want to release additional data to facilitate contact tracing, they can already do so. Typical methods could include browsing their social media history, checking their calendar, or reviewing navigation data. With the research identified in this section, and the importance various authors placed on various aspects, it is possible to come up with a list of requirements for contact tracing applications-a framework. However, two problems remain: First, some requirements find their origin in untested research. Second, if the decentralised Google and Apple API is the best option for contact tracing, will it survive that framework? Does the Google and Apple implementation comply with the research identified so far? Additionally, the role Google and Apple play is debatable. What are they going to do with the technology they designed once the crisis is over? The same question needs answering from a governmental perspective: Somewhere, a policymaker in law enforcement already considers using this technology for law enforcement purposes. Since contact tracing is dealing with sensitive information, this information needs to be protected against well-known attacks. Understanding the attack vector against such applications is important in securing them. Investigating the threats against both centralised and decentralised systems are demonstrated in [9; 26]. It was argued that neither system protects privacy and security [9] (i.e., tracking, social graphing, identification, pressure to opt-in, replay attacks, etc. ), as shown in Figure 1. Some of the threats against decentralised systems include tracking people by de-pseudonymising user's EphID, disclosing the social graph, identifying diagnosed people, pressure to opt-in, and injecting false encounters. Centralised systems suffer from similar threats. Figure 1: Overview of privacy and security attacks.