# Blockchain-Based Evidence Trustworthiness System in Certification
## 5 Validation and Results
### Cybersecurity Certification
This audit trail has been particularized to the certification domain considering the main particularities of evidence risk management (integrity, transparency, availability) and the essential requirements of a certification process (sensitive information confidentiality, contextual information, and automation). In this way, the risks identified in Section 3 are mitigated as explained in Table 7.  
Figure 8: Integrity verification service for recorded evidence. Figure 9: Integrity verification service filters definition. Regarding the performance, this will mainly depend on the specific features of the underlying Blockchain network. In particular, the following aspects are significant:  
* Consensus mechanisms: These have traditionally been time-consuming, such as the Proof of Work used in Bitcoin. However, current solutions include simpler and faster alternatives, especially in permissioned networks such as that suggested for the trustworthiness system [48; 49]. In this validation, the Raft consensus algorithm was considered with the default configuration [50]. Raft is well adopted in private networks such as Quorum due to its good performance and scalability [51]. * Network Congestion: A congested network can cause high delays. However, permissioned networks are usually less congested because only a group of authorized participants can join the network, which reduces the number of nodes that need to validate transactions. This reduces overhead and improves efficiency [52]. In this validation, the deployment of a dedicated Quorum network ensures no congestion. However, in real-world implementations, such as the potential deployment in EBSI where the Blockchain network is shared by multiple services, some level of congestion is anticipated. * Block size: A larger block can contain more transactions, but it can also increase processing time and latency. This is a configurable parameter determined by the Blockchain technology that needs to be optimized [53]. In this validation, the 64 kB default value for Quorum was considered. As the data to be recorded in the trustworthiness system (evidence and assessment result) is always lower than  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Attack** & & **Justification** \\ \hline \multirow{4}{*}{Eavesdrop on evidence storage connection} & \(\bullet\) & No sensitive information is recorded in the trustworthiness system; only information hashes and contextual information is recorded. \\ \cline{1-1}  & \(\bullet\) & Blockchain avoids information modifications/removals by design. Even if someone managed to write, modify or delete information, there would always be a trace of the actions performed, so that it would be possible to detect what had happened. Consequently, Blockchain-based systems are considered a trusted source of information. \\ \cline{1-1}  & \(\bullet\) & Blockchain is distributed and decentralized, evidence hash a very high availability and DoS attacks have little success. 1 kB considering the data model in Figure 6, a block can contain several transactions, improving the performance. As can be seen, the fact that the proposed trustworthiness system is based on a permissioned network improves the performance and avoids unnecessary delays. In a real-world deployment, the configuration parameters need to be optimized in order to achieve improved performance.