  In modern healthcare systems, being able to share electronic health records
is crucial for providing quality care and for enabling a larger spectrum of
health services. Health data sharing is dependent on obtaining individual
consent which, in turn, is hindered by a lack of resources. To this extend,
blockchain-based platforms facilitate data sharing by inherently creating a
trusted distributed network of users. These users are enabled to share their
data without depending on the time and resources of specific players (such as
the health services). In blockchain-based platforms, data governance mechanisms
become very important due to the need to specify and monitor data sharing and
data use conditions. In this paper, we present a blockchain-based data sharing
consent model for access control over individual health data. We use smart
contracts to dynamically represent the individual consent over health data and
to enable data requesters to search and access them. The dynamic consent model
extends upon two ontologies: the Data Use Ontology (DUO) which models the
individual consent of users and the Automatable Discovery and Access Matrix
(ADA-M) which describes queries from data requesters. We deploy the model on
Ethereum blockchain and evaluate different data sharing scenarios. The
contribution of this paper is to create an individual consent model for health
data sharing platforms. Such a model guarantees that individual consent is
respected and that there is accountability for all the participants in the data
sharing platform. The evaluation of our solution indicates that such a data
sharing model provides a flexible approach to decide how the data is used by
data requesters. Our experimental evaluation shows that the proposed model is
efficient and adapts to personalized access control policies in data sharing.
