# Privacy-Aware Access Protocols for MEC Applications in 5G +
## 4 Results and Discussion
### Unlinkability
#### 4.2.2 Dependent Cases  
In Section 3.3.2, we identified which privacy requirements are applicable for the dependency combinations. Now, we analyze how the solution in Section 4.1 meets the applicable privacy requirements for dependent cases. How our solution fulfills the privacy requirements for outsiders of the first two types (parties non-visible in the system model and other MNO subscribers than Alice) is not affected by the dependency between the parties participating in the protocol. For that reason, our solution fulfills requirements R15-R20 in the case of the first two types of outsiders for all dependency cases in the same way as for the case where all parties are independent. Let us now consider the third type of outsiders, i.e., the other MEC applications inside the same MEC host, where APPIFY is located. It can be possible that some other MEC applications are dependent on MNO, MEC, or APPIFY, e.g., these parties have their own applications in the MEC host. As an example of how such dependency may have an effect on privacy, assume that [PERSON] establishes two DTLS sessions from the same device, which also has the same IP address, to APPIFY and another MEC application. Suppose the MEC host is dependent on this other MEC application. In that case, MEC knows that the same user is establishing the two DTLS sessions, and the other MEC application knows that its user, say, [PERSON], also uses APPIFY with some username. However, the combination of the MEC host and the other MEC application still cannot conclude that this username [PERSON], even if they somehow see that [PERSON] is active on APPIFY. This example shows that collaboration between the MEC host and some MEC application could reveal some hints about communication between Alice and APPIFY. However, obtaining such indirect information still depends on coincidences, and therefore it does not change substantially how our solution fulfills the requirements about MEC. The collaboration of MNO and other MEC applications would not provide many benefits because the MEC host is between MNO and the other MEC application. Finally, if APPIFY collaborates with some other MEC application, these two applications can be considered only one service, where the other MEC application is just an extension of APPIFY. In summary, none of the possible dependencies between other MEC applications and parties that provide a service to Alice have a substantial impact on how our solution meets the requirements. The dependence of two out of three parties (MNO, MEC, and APPIFY) would not impact the privacy requirements of the independent party. For example, in the case where MEC and APPIFY are dependent, the requirements for MNO, R1-R5, are fulfilled by the solution similarly as when all three parties are independent. This is because the dependency of MEC and APPIFY does not help MNO to obtain any extra information. Likewise, the dependency of MNO and APPIFY does not change how the privacy requirements for MEC, R6-R10, are fulfilled. Furthermore, the dependency of MNO and MEC does not affect how the solution fulfills the privacy requirements for APPIFY, R11-R14. MNO and MEC Combination  
Combining with MEC does not help MNO, and vice versa, to obtain information that APPIFY has because of the secure channel between Alice and APPIFY in the solution. Therefore, the applicable requirements R2, R3, R5, R6, R8, and R10 are fulfilled similarly to how they are fulfilled in the independent case. MNO and APPIFY Combination  
Combining with APPIFY would clearly help MNO to identify that [PERSON] is using APPIFY, but that would not help to determine which other MEC applications [PERSON] or another user might be using. Therefore, the requirements R1, R4, and R5 are partially fulfilled. APPIFY would also help MNO to identify what [PERSON] is sending to and receiving from APPIFY and help APPIFY to identify IMSI and the device from which it receives messages. Hence, the solution does not fulfill R2, R3, R11, R12, R13, or R14 in this combination.