# Results and Achievements of the ALLIANCE Project: New Network Solutions for 5G and Beyond
## 5 Trust Element  
### Introduction  
In some situations, network operators need to exchange different kinds of information among them. For example, in the context of 5G networks, operators may want to exchange the locations of 5G subscribers in their respective networks, to locate roaming user devices [44; 45]. Another example is some SDN deployments that leverage overlay networks that must maintain a database of overlay addresses to underlay addresses (usually called Mapping System [46; 47]). In addition, this information can be more complex, such as access control policies or QoS information.  
However, exchanging this information between networks in different administrative domains requires trusting external networks (Figure 3). In other words, network A has to accept information from the external network B that can potentially influence routing behavior in network A. Hence, this situation is sometimes judged inappropriate by some operators [48].  
The current solutions to transfer this information are usually complex to operate, e.g., in the area of Mapping Systems LISP-TREE [49] is similar to the DNS in configuration complexity. In addition, if we want to add security properties to such systems, such as confidentially or authentication, we must leverage centralised systems, i.e., Certification Authorities (CAs) to manage digital certificates. Although CAs are extremely convenient for single administrative domains, their centralisation is not convenient for a scenario with multiple administrative domains, because a single party can change the status of the database. There exist some distributed alternatives to centralised CAs, but they require complex configuration or do not scale well, such as cross-certification or bridge CA certificates [50; 51].  
On the other hand, blockchains have a decentralised trust architecture. Each participant of the blockchain has full control of its database entry, and it cannot be modified by  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Domain Name** & **Application** & **Accuracy (\%)** \\ \hline drive.google.com & Google Drive & 95.4 \% \\ mail.google.com & Gmail & 94.7 \% \\ netflix.com & Netflix & 97.3 \% \\ web.whatsapp.com & WhatsApp web & 89.2 \% \\ youtube.com & YouTube & 87.8 \% \\ \hline \hline \end{tabular}
\end{table}
Table 1: Per-application accuracy achieved by the proposed classification system (processing only packets transmitted in the first 40 ms of web and encrypted flows). Summary of experimental results from [37]  
Figure 3: Exchange of routing information between two networks in different administrative domains. The Mapping System is a server that stores overlay-to-underlay mappings, and other network metadata.  
the other participants. Taking this into account, we have proposed leveraging the inherent decentralisation of blockchains to exchange information between different trust domains in a decentralised way (Figure 4). Thanks to the properties of blockchains, we can provide a shared database among a set of cooperating network operators that do not necessarily trust each other. At the same time, the data from each operator is protected from modification by the other operators.