  With the advent of the Internet of Things (IoT), e-health has become one of
the main topics of research. Due to the sensitivity of patient information,
patient privacy seems challenging. Nowadays, patient data is usually stored in
the cloud in healthcare programs, making it difficult for users to have enough
control over their data. The recent increment in announced cases of security
and surveillance breaches compromising patients' privacy call into question the
conventional model, in which third-parties gather and control immense amounts
of patients' Healthcare data. In this work, we try to resolve the issues
mentioned above by using blockchain technology. We propose a blockchain-based
protocol suitable for e-health applications that does not require trust in a
third party and provides an efficient privacy-preserving access control
mechanism. Transactions in our proposed system, unlike Bitcoin, are not
entirely financial, and we do not use conventional methods for consensus
operations in blockchain like Proof of Work (PoW). It is not suitable for IoT
applications because IoT devices have resources-constraints. Usage of
appropriate consensus method helps us to increase network security and
efficiency, as well as reducing network cost, i.e., bandwidth and processor
usage. Finally, we provide security and privacy analysis of our proposed
protocol.
