Due to the exponential growth in the number of Internet of Things (IoT) devices that generate and collect data over the network, security presents significant challenges. It is crucial to ensure the integrity and security of IoT devices as well as to address issues such as interoperability and trust in data sources. Traceability and the ability to audit events and transactions play a fundamental role in achieving these goals.

In the proposed paper, we present a novel architecture together with its implementation as a proof-of-concept of a traceability and auditing IoT system based on a Distributed Ledger Technology (DLT). To demonstrate the applicability of the proposed solution, a smart contract-based system for occupational risk prevention (ORP) has been developed to monitor oxygen concentration in confined spaces that exist in ships and shipyards.

The system has been devised for the operators that weld inside the ships of the Spanish shipbuilding company Navantia, which is one of the largest shipbuilders in the world. Specifically, the IOTA network has been used, which benefits the system through its decentralized, secure, and scalable data structure. In addition, the integration of smart contracts allows for establishing predefined rules and conditions, ensuring the execution of logic in a reliable and automated manner. By combining these technologies, it is possible to develop a transparent, dependable and tamperproof system for IoT traceability and auditing. To demonstrate the viability of the system, it has been tested in one of the shipyards that Navantia owns in Ferrol, showing good performance and reliability.