# Overview of Blockchain Oracle Research
## 5 Converging Studies, Research Themes, and Research Directions
### Oracle Applied
SCOs are, in fact, able to sense the surrounding environment and efficiently communicate the information acquired. Lastly, they have the autonomy to respond to certain situations based on predefined rules. [PERSON] and [PERSON] [98] proposed network operator companies as tracking oracles given the massive presence of cellular radio towers. Finally, [PERSON] et al. [102] discussed the issue of attaching a physical product to the blockchain in order for it to be traced by an oracle. Studies from the University of Verona have also investigated this specific aspect [8; 103]. All of these studies support the idea that a known oracle identity is fundamental to achieving this task. For healthcare, only four papers were retrieved and were all focused on the security and access control of patients' records [104; 105]. [PERSON] et al. [105] proposed a decentralized reputation-governed trusted oracle network for patient records to promote competition among oracles and ensure quick and reliable data transmission. However, they also proposed that, because of the sensitive nature of data transmitted, oracles should be approved by a regulatory agency. In a subsequent study in which they proposed a system of tokens to ensure patients' control of their medical records, they also debated the necessity of having a second oracle type for a time-based trigger events [104]. Research by [PERSON] et al. [106] focused on the same objective but proposed a specific oracle solution with the Chainlink oracle provider and Ethereum blockchain. Seven entries regarding applications in AI were retrieved. The central focus was to exploit automation and oracles to guarantee trust in data gathering and processing. As in the original idea of the software oracle problem, the objective was to reduce external parties' intervention in automated procedures. Studies from Toulouse University and INRS Montreal investigated AI-based oracles to provide non-forged results [107; 108]. While the first aimed to complete the automation of the oracle ecosystem, the second proposed a more hybrid system between humans and machines. In particular, [PERSON] et al. [107] demonstrated that the presence of a third party, a human or social robot, plays an important role in a blockchain-enabled trust game. The works of [PERSON] et al. [109] and [PERSON] et al. [110] aimed to exploit blockchain oracle features to improve machine learning processes and predictive models to reduce dependency on third-party data feeds. Both offered a theoretical overview of the blockchain implementation outcome at the concept stage. The IoT sector has 12 publications, and the main issue of investigation is the problem faced while ensuring that the data gathered by IoT devices are trustworthy and private. [PERSON] [111] and [PERSON] et al. [112] outlined the problem of secure and trustworthy data provenance within IoT systems. The first focuses on the problem of the authentication of IoT oracles on blockchains to ensure that data are submitted only by trusted oracles. It proposes that oracles submit their addresses along with data so that blockchain applications can easily verify data provenance. The second is focused on the statistical probability for an IoT oracle to deliver reliable data to the blockchain. In response to this issue, [PERSON] et al. [113] proposed a secure and lightweight triple-trusted architecture to guarantee the unforgeability of data collected by trusted oracles. In their research, however, the premise is that oracles are trustworthy in the first place. By contrast, contributions from Khalifa University and Insubria University approached the confidentiality of the IoT. The first proposes implementing cloud computing and different access privileges to guarantee against unwanted data leakage. The second proposes an encryption model in which IoT and related data are only accessible by the intended users [114; 7]. Whereas the first is more oriented toward the technical feasibility of IoT-based blockchain data gathering, [PERSON] et al.