The development of ICTs (Information and Communication Technologies) and the usage of personal data for both research and commercial purposes over the last years have brought the question of the protection of personal data. The GDPR (General Data Protection Regulation) has defined the ways how personal data should be treated, but the application of these requirements still remains an open issue. This paper is dedicated to the research of the blockchain advantages when it comes to providing the transparency of the usage of personal data and provides proof of concept where it demonstrates the application of blockchain in working with users' consents. Hyperledger Fabric was chosen as the development platform which proves as a suitable choice when it comes to achieving transparency, immutability, and modularity.
Due to the faster development of technology and the usage of information systems
over the last years, the protection of personal data has become more important than
ever. Numerous organizations collect data from citizens for a variety of purposes,
both research and commercial. The results of data analysis can have a great impact on
society, but on the other hand, citizens should be informed at any moment how their
data is collected and processed in order to avoid various data malversations. The
emergence of GDPR[
Blockchain advantages in terms of achieving transparency and immutability and the Hyperledger Fabric as the chosen blockchain platform will be discussed in the next section. After that, the implemented blockchain network for keeping logs of users' consents will be presented and some future work will be addressed. 2
Blockchain has received wide recognition upon the occurrence of cryptocurrencies, such as Bitcoin and Ethereum. It was spread later to smart contract techniques, programs that contain a transaction logic needed for updating the state on the ledger and use completely distributed data storage and processing, without the central authority. As the popularity of blockchain grew, it went beyond the scope of usage within cryptocurrencies and found a new field of application in various enterprise use cases. The immutability of blockchain is based on hash cryptography, which ensures that blocks creating a blockchain network cannot be modified or tampered with. Being a distributed ledger, it eliminates a single point of failure which exists in centralized systems and also removes the need for trusting one central authority. Having the aforementioned characteristics, blockchain has proven as a convenient area of research when it comes to establishing transparency and immutability of personal data.
While numerous well-known blockchain platforms are currently being adapted to
enterprise use cases, Hyperledger Fabric [
The developed platform consists of a client application and a Hyperledger Fabric network which communicate using the Fabric SDK for Node.js. 3.1
The client application is implemented in Node.js and has two most important roles: assigning a digital identity to all users who want to participate in the Hyperledger network and sending requests from users to the network. The identity assignment is done between the client application and Certificate Authority, the body that issues digital certificates to different parties. Each user that wants to participate in the network has to go through the registration and enrollment process with Certificate Authority. When these two steps are completed, the user is assigned a digital certificate which is stored in the user's wallet along with his private key. For the purpose of testing the wallet is stored in the file system. However, storages such as databases and hardware security modules should be considered for the deployment. The certificate is sent with each request to the network so that the user can be appropriately identified. 3.2
As regards the Hyperledger Fabric network, two organizations were created, each one having one peer that form a channel. Peers, smart contracts and certificate authorities run inside docker containers. The smart contract consists of methods that perform basic operations working with users’ consents: creating/reading/modifying/deleting a consent, reading all consents, reading a history of consents. The consent contains the following attributes: data subject, creation date, data category, purpose, and recipient. For monitoring the activity on the underlying blockchain network Hyperledger Explorer tool is used, which supports the visualization of the network, blocks, and transactions (Fig. 1).
The Hyperledger Fabric has proven to be a suitable choice for developing the desired platform because of the advantages for implementing the client application and smart contracts in general-purpose languages, with good support of the Fabric SDK. Furthermore, the modularity of Hyperledger Fabric allows usage of different databases for storing the world state of the platform which has proven useful while implementing this network since the initial approach was to use the LevelDB database, but with the later need for rich queries, it was replaced with the CouchDB. The future work would include testing the performance of the network by using the Hyperledger Caliper, a benchmarking tool provided by Hyperledger community.
The research presented in this paper is partly financed by the European Union (H2020 TRAPEZE project, Pr. No: 883464, H2020 LAMBDA Project, Pr. No: 809965), and partly by the Ministry of Education, Science and Technological Development of Republic of Serbia.