###### Abstract  
A high level of data integrity is a strong requirement in systems where the life of people depends on accurate and timely responses. In healthcare emergency response systems, a centralized authority that handles data related to occurring events is prone to challenges, such as, e.g., disputes over event timestamps and data authenticity. To address both the potential lack of trust among collaborating parties and the inability of an authority to clearly certify events by itself, this paper proposes a blockchain-based framework designed to provide proof of integrity and authenticity of data in healthcare emergency response systems. The proposed solution integrates blockchain technology to certify the accuracy of events throughout their incident lifecycle. Critical events are timestamped and hashed using SHA-256; then, such hashes are stored immutably on an EVM-compatible blockchain via smart contracts. The system combines blockchain technology with cloud storage to ensure scalability, security, and transparency. Blockchain technology provides the advantage of eliminating a trusted server, providing timestamping and reducing costs by forgoing such a service. The experimental results, using publicly available incident data, demonstrated the feasibility and effectiveness of this approach. The system provides a cost-effective, scalable solution for managing incident data while keeping a proof of their integrity. The proposed blockchain-based framework offers a reliable, transparent mechanism for certifying incident-related data. This fosters trust among healthcare emergency response system actors. e +
Footnote †: journal: Future Internet  
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disputing parties. e.g., the challenging authority could argue that the data were tampered with in certain circumstances, making it appear that the ambulance arrived on time. In such cases, the defendant would not be able to demonstrate otherwise. Although a centralized database would be under the control of some authority, when no authority can be considered trustworthy, blockchain technology is apt to ensure data integrity and access control, thanks to its mechanisms based on cryptographic signatures and hashes that confirm that the recorded data remain unmodifiable [1]. Several blockchain applications have been proposed for healthcare systems, including the management of electronic health records (EHR) and patient data [2; 3; 4], emergency medical services [5; 6], patient-centric data sharing [7; 8], integration with IoT devices [9], clinical research [10; 11], healthcare security and audit processes [12; 13; 14; 15], and medical data sharing [16; 17; 15]. Certainly, patient confidentiality and secure data exchanges should be ensured [18]. Unlike methods that depend on trusted third parties or centralized timestamping servers, our framework leverages a blockchain model to eliminate such dependencies. In our solution, blockchain-stored hashes either provide a certification of data kept unaltered in the database or make alteration evident and easily detected. Previous blockchain-based timestamping approaches have not solved issues due to transaction delays, high costs, and privacy. Our dual-layered design, which combines real-time cloud storage with blockchain recording, resolves these issues by ensuring both efficiency and robust security even under high data loads. Importantly, our approach uniquely ensures non-repudiation of recorded events, a critical capability in healthcare incident response that, to the best of our knowledge, has not been addressed by previous solutions. We propose a blockchain-based framework designed to certify the integrity and authenticity of data and their timestamps for events occurring in healthcare emergency response systems. The proposed system includes a health emergency aggregator (HEA), a software component that collects incident data, records such timestamped data on a cloud server, and hashes them using SHA-256, as soon as they occur.