# Decentralized and Secure Blockchain Solution for Tamper-Proof Logging Events
## 2 Related Work
Another work [17] proposes using Hyperledger as a private blockchain, where smart contracts manage the transactions and the information associated with events is stored on-chain. This open-source project is specifically designed for IoT devices and focuses on their security. However, the transparency and reliability of a private network differ significantly from those of a public blockchain. Furthermore, [18] proposes a blockchain-based service used in supply chain and logistics management, also known as Logchain Logistics as a Service (LCaaS). This service is divided into two levels of hierarchy to achieve scalability. The first one stores signatures on a blockchain that can be either public (i.e., Ethereum) or private (i.e., IBM blockchain), while the data corresponding to the signatures is stored both off-chain and on-chain. However, the service makes it impossible to certify that said data have not been modified before inclusion when the log files are stored on the chosen blockchain. Another study has presented a Blockchain-Enabled Scalable Network Log Management System [19]. This system utilizes Multichain to store hashes, timestamps, and ownership data while employing the InterPlanetary File System (IPFS) to store complete logs. It also features a query mechanism that enables efficient retrieval and verification of logs. This effectively addresses the limitations often encountered in other blockchain-based log management systems, which typically lack structured search capabilities. However, similar to previous examples, relying on a private blockchain may diminish the overall transparency and reliability of the system. In [20], a decentralized data storage network is introduced, utilizing a custom-built blockchain written in Go to prevent data manipulation. This system employs a PoW consensus mechanism to maintain data integrity and uses a Gossip Protocol for automatic block repair, enabling nodes to detect inconsistencies and retrieve valid copies of the blockchain from their peers. The data are stored on-chain to ensure immutability and an API Gateway facilitates log transactions through RESTful API endpoints. Nevertheless, being a private and custom blockchain raises concerns regarding transparency and reliability. Finally, a blockchain-based audit log system has been proposed to ensure the data integrity of log files [21]. The system assumes that both loggers and auditors may be untrustworthy and mitigates these risks by utilizing smart contracts within Hyperledger Fabric. This method presents a way to generate on-chain integrity proofs using Non-Fungible Tokens (NFT), with log files stored off-chain in the IPFS. While this system enhances scalability and security, it is limited to a permissioned blockchain, which may decrease transparency compared to public blockchain solutions. Table 1 presents a comparison of the previous solutions compared to the approach presented in this paper. It should be noted that only our solution and the one presented in [11] use the Syslog standard as a data source to ensure compatibility and interoperability with numerous tools and applications designed to work with this standard. It is also worth noting that most of the proposed works use private networks due to the cost of storing data in public blockchains, implying less transparency in the process. On the other hand, only [11; 15; 19] use some additional tools to visualize the stored information in a user-friendly way, as in the proposed solution. Finally, it is worth highlighting the open-source nature of the proposed system together with the proposal of [18], which allows transparency and facilitates project release for reproducibility within the scientific community, aiming to establish a standard for storing registries in the blockchain. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Reference** & **Data Storage** & \begin{tabular}{c} **Kind of** \\ **Blockchain** \\ \end{tabular}  & \begin{tabular}{c} **Consensus** \\ **Algorithm** \\ \end{tabular}  & **Transfer** &