# Contact Tracing: Ensuring Privacy and Security
## 5 Framework Evaluation  
It is worth noting that this research used three leading European implementations, which are not only currently in use but also were subjected to a lot of attention and debate. These implementations are Corona-Melder (i.e., the Netherlands), Corona-Warn-App (i.e., Germany), and SwissCovid (i.e., Switzerland). These Apps are mature and well-received within the privacy research community [19]. Now, let us revisit the questions in Table 3 and \begin{table}
\begin{tabular}{c c c} \hline \hline
**Research Question,** & **Identifier,** & **Method** \\ \hline Can infected users be re-identified on & 1.2 & Review Implementation \\ uploading TEKs by sniffing their traffic? & 1.2 & Review Implementation \\ \hline Can users be identified by IPs on & 1.2 & Review Implementation \\ uploading TEKs? & 2.1 & Review Implementation \\ \hline Is Bluetooth the only sensor used in & 2.1 & Review Implementation \\ the application? & 3.1 & Review Implementation \\ \hline Does the implementation have a PIA & & \\ approved by the national & 3.1 & Review Implementation \\ privacy authority? & & \\ \hline Is the application voluntary? & 3.2 & Review Implementation \\ \hline Does the backend store data exclusively in & 3.4 & Review Implementation \\ the EU? & 3.4 & Review Implementation \\ \hline Does the implementation follow a security & & \\ standard ensuring continuous & 4.1 & Review Implementation \\ security assessment? & & \\ \hline Can the source code be reviewed? & 4.2 & Review Implementation \\ \hline Does the downloadable app match the & 4.2 & Review Implementation \\ source code published? & 4.3 & Review Implementation \\ \hline Can GAEN API be reviewed? & 4.3 & Review Implementation \\ \hline Are reply attacks possible? & 1.4 & Literature Review \\ \hline Did the government have plans to & 3.2 & Literature Review \\ dismantle the system after the pandemic? & 3.3 & Literature Review \\ \hline Do Google and Apple have plans to & 3.3 & Literature Review \\ dismantle GAEN after the pandemic? & 1.1 & Experiments and \\ \hline Can users be tracked by Rolling Proximity & 1.1 & Literature Review \\ Identifier (RPI)? & 1.2 & Experiments \\ \hline Can users be re-identified by RPIs analysis? & 1.3 & Experiments \\ \hline Can users be pressured into disclosing & 1.3 & Experiments \\ compromising data? & 2.3 & Experiments \\ \hline Are the BLE beacons pseudonymous and & & \\ do they rotate frequently? & 2.3 & Experiments \\ \hline Are Bluetooth hardware addresses in the & & \\ advertisement data random and & 2.3 & Experiments \\ rotate frequently? & & \\ \hline Is it possible to profile users? & 1.5 & Experiments \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Questions to evaluate implementations. answer them. It is worth emphasising that, this paper focuses on those questions requiring experimentation (i.e., see Table 3), thus experiments were performed using a Raspberry Pi 4 running Raspbian Linux and an Ubertooth Bluetooth interception module. Different mobile handsets are used in such experiments. _Can infected users be re-identified on uploading TEXs by sniffing their traffic?_ Uploading TEXs is a sign of infection since it creates traffic to a server that is normally absent. This attack works even if traffic is encrypted. To negate this threat, the Dutch and German implementation upload fake keys at random intervals. If an attacker sniffs the traffic between the handset and the server, it is impossible to separate real uploads of keys from fake keys. This implementation prevents an attacker from identifying infected users by sniffing the TCP/IP traffic between the handset and the server. _Can users be identified by IPs on uploading TEXs?_ If an attacker compromises the backend server, it is possible to re-identify infected people by IP address. This only works when it is possible to combine the IP address with infection data. The Dutch and German implementations separate the IP address from the TEXs as soon as traffic arrives at the backend server [27].