# Decentralized and Secure Blockchain Solution for Tamper-Proof Logging Events
## 1 Introduction  
Log files are used as a control mechanism to detect security incidents, policy violations, regulatory compliance, and operational problems in computer applications. These logs contain information about specific events on an organization's networks or systems. They provide both the current states of the systems and the traceability of the actions performed on the network devices, providing a detailed description of their behavior. Logs are therefore essential for forensic investigation and security auditing, such as compliance with regulations and standards like the Health Insurance Portability and Accountability Act (HIPAA) in the United States or the General Data Protection Regulation (GDPR) in the European Union [1]. Different organizations are defining diverse standards for managing log events that lack global uniformity. This is the case for the regulations to which a sector is subject in a specific country (e.g., Law 25/2007 in Spain) or the international standards such as PCI DSS (Payment Card Industry Data Security Standard). Either way, different types of logs include audit logs, whose primary purpose is to track changes made to systems or their behavior during use, and application logs, written by applications indicating what happens at runtime [2]. One of the classic challenges in log management is preserving the integrity of stored information to ensure its availability and reliability. Data can be subject to threats from third parties, such as encryption, rendering it unusable through ransomware infection, alteration, or content deletion to cover the trace of cybercriminals, as well as manipulation of information by insiders seeking to take advantage of a situation. Therefore, it is recommended to follow a proactive Zero Trust approach that ensures trust in log records about events occurring in our network rather than automatically relying on the trust of a user, device, or network [3]. Recently, blockchain technology has become popular as it provides secure, decentralized data storage. However, other inherent characteristics of this technology, such as immutability or complete traceability of the stored data, have also generated interest in its potential use. Consequently, researchers have conducted several studies on utilizing blockchain for storing certain types of data, such as access, configurations, or payments [4]. Given these precedents, the present hypothesis posits the potential use of a public blockchain to certify the integrity, immutability, and non-repudiation of the system's activity log messages. By leveraging this technology, it may be possible to establish a reliable and secure system for recording and verifying data, thereby enhancing the trust and transparency of the overall system. Therefore, this solution has the potential to be universally adopted as an openly auditable service by organizations looking to reinforce their existing logging infrastructures while ensuring critical audit events remain tamper-proof. In the related work, several blockchain-based approaches have been proposed to ensure the integrity and immutability of log events. Some solutions, such as Exonum and Hyperledger, employ private blockchains to offer improved control; however, they encounter issues related to reduced transparency and centralized trust. Alternatively, solutions based on public blockchain, like Bitcoin, provide a high level of security but are limited by high transaction costs and scalability challenges. The proposed system addresses these limitations by implementing a decentralized, open-source log storage mechanism that utilizes public blockchains optimized for cost efficiency and transaction speed. Unlike previous methods, the proposed solution can effectively manage a substantial rate of log events on public blockchains, thereby enhancing trust, transparency, and compliance with industry regulations while ensuring practical deployment feasibility.