# Multidimensional Study on Users' Evaluation of the KRAKEN Personal Data Sharing Platform
## 1 Introduction  
In recent years, blockchain technology promises to return Internet users control over their personal data [1], and this might pave the way to a more user-centered management of personal data [2] in several application domains such as healthcare and education. Blockchain is a decentralized ledger where data storage, validation, and synchronization can only be completed when all the contributing system participants (i.e., nodes) contribute their computational capacity [2, 3]. Blockchain-based systems can significantly decrease the risk of data breach, falsification, and tampering, protecting data security and privacy to a level that other existing systems are unable to reach [4]. Thus, providing Internet users with blockchain also provides individuals with the opportunity to share personal data at their discretion with interested third parties, while privacy and security risks are minimized [5, 6]. In this paper, we refer to third parties as any stakeholders holding interest in individuals' health or education data, such as medical researchers, pharmaceuticalcompanies, digital health companies, universities, and employers. These third parties, as key players in the Internet ecosystem, may require assess to an individual's data for their organizational activities, though they should avoid collecting and exploiting the data without the individual's consent or sharing the data in a way that jeopardizes the individual's privacy [7,8]. Although studies have shown that individuals are generally not opposed to data sharing with these third parties [7, 8, 9], the concerns about privacy and security are growing, and individuals demand greater transparency as to who can access their data after they are shared and for what purposes the data are used [8, 9, 10]. Since blockchain can combine cryptography with smart contracts (smart contracts being small bits of code that embed procedural logic, which is automatically executable), blockchain-based systems can ensure that it is individuals who initiate data sharing. This capability allows individuals to determine which data to share with which third party and under what conditions [5, 9, 10, 11, 5, 6, 7, 8, 9, 11], preserving their privacy and their right to be informed in a more transparent way. In addition, smart contracts can be combined with data tokenization, the transformation through cryptography of data into discrete objects that can be transferred over a blockchain network. Blockchain-based systems can offer individuals the possibility of being rewarded for sharing personal data. In this way, users can be more motivated to actively share data with third parties, such as researchers and digital health companies, which can greatly benefit medical research and care management [12,13]. The data can be tokenized, and the third parties may pay for the data use with cryptocurrency or other value tokens. Due to the series of advantages provided by blockchain-based data sharing systems, researchers' interest for blockchain architecture and platform deployment is growing [6, 7, 8, 9, 10, 11, 12, 13, 14]. However, both academics and practitioners have mainly focused on the technical components of blockchain-based data sharing systems and have conducted these studies mainly from the perspective of institutional data providers and consumers. Very little is known about individuals' intentions to adopt the blockchain-based system, specifically whether they perceive themselves as motivated to take, and capable of taking, greater control of personal data sharing; what concerns they may have about blockchain-based data sharing systems; and how these concerns can be addressed to remove barriers to adoption. Shading light on these matters is key to inform researchers and practitioners about the issues that need to be considered when designing a blockchain-based data sharing system, to deploy a real user-centered design approach [15].