After several incident in which the privacy of patients was violated, the need for
logging of access to medical data is evident. In this master thesis, the first prototype is presented for a blockchain-based access log for medical data. This prototype
uses a novel blockchain to create a tamper-proof log. Patients each have their own blockchain in which health care providers can participate as well. At any time, a user can check the access logs of their data on the online MediTrail portal. Users can also validate an entry by placing a digital signature. The prototype performs well when no consensus algorithm is used. Achieving consensus with Proof of Elapsed Time slows adds overhead. The prototype succeeds in providing the patient with knowledge and power over their data in the form of a tamper-proof auditable access log.