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cess and requires a high computation power. Besides,
transaction processing time mainly depends on the
number of available miners willing to mine the pend-
ing transactions, which currently can take up to 5 min-
utes.
The MedRec (Azaria et al., 2016) work was later
continued by the authors in (Nchinda et al., 2019).
The authors replaced miners with a network of trusted
providers that participate in a proof of authority con-
sensus mechanism. They used blockchain to store
permission contracts. In their work, providers can
join the network and grant patients, and other entities
access to their databases using their credentials.
The authors in (Mikula and Jacobsen, 2018) used
a federated and private blockchain to explore an
auditable identity and access management frame-
work for EHR systems. Evaluation of their system
showed a size of 3.8 MB for the initialization of the
blockchain with 2-3 seconds of mining time for new
transactions.
The authors in (Chen et al., 2019) presented an in-
tegration of a cloud and blockchain storage scheme to
manage PHR data. They used off-chain cloud stor-
age for storing a large amount of medical data and the
blockchain for indexing and securing them. In their
work, patients are in control of their data. However,
the interoperability of their system is not examined.
In (Abouzahra, 2019), the authors proposed an in-
teractive model for a blockchain-based PHR system.
In the proposed system, smart contracts are utilized to
collect patients’ health records, and blockchain tech-
nology is used to make transactions immutable and
traceable. The authors claimed that their approach
encourages physicians to have more engagement with
their patients outside clinics resulting in better care
delivery.
3 DEFINITIONS
There are two types of blockchains: permissionless
(public) and permissioned (private/consortium) (Al-
hadhrami et al., 2017). Depending on the need, each
blockchain type has its advantages and disadvantages.
In public blockchains, anyone can join the net-
work, invoke transactions, write new blocks, and con-
tribute to the maintenance of the network. On the one
hand, this feature adds transparency to the data and
makes the data extremely secure and immutable. On
the other hand, redundancy in the network makes the
network slower and increases the maintenance cost,
significantly. Public blockchains are most suitable for
public digital assets such as cryptocurrencies, where
everyone needs access to read the ledger. However,
this level of transparency might endanger the pri-
vacy of users. Bitcoin(Nakamoto et al., 2008) and
Ethereum (Wood et al., 2014) are two well-known ex-
amples of public blockchains.
On the contrary, permissioned blockchains only
allow the pre-authorized participants to maintain the
ledgers and give access or add users to the network.
Permissioned blockchains can easily scale and have
significantly faster transaction processing time in ex-
change for the anonymity of the users. Further, since
the ledger is not open to the public, users in the net-
work have a higher level of privacy. Permissioned
blockchains can be categorized into two types: pri-
vate and consortium. In private blockchains, only one
participant has the right to add blocks to the chain or
allow others to read the transactions. In consortium
blockchains, a set of organizations control the consen-
sus process. Also, blocks can be added to the chain
only if the predefined nodes reach a consensus. For
an EHR system, a consortium blockchain is more ap-
pealing mainly because of the faster transaction pro-
cessing time and the higher level of privacy that it of-
fers to the participants in the system.
There are two major frameworks for deploying
a consortium blockchain network: 1) Quorum(quo,
2019), which is an enterprise-focused version of
Ethereum, and 2) Hyperledger Fabric(Androulaki
et al., 2018), a product by Linux Foundation which
is supported by enterprise companies like IBM, In-
tel, and SAP. In our work, we use Hyperledger Fabric
for model implementation because of its bigger com-
munity of developers, support from large enterprise
companies, and a wide variety of APIs.
There are five main concepts in a Hyperledger
Fabric model: assets, participants, transactions,
chaincodes, and access control lists (ACLs). Partic-
ipants are the users involved in the model, such as
patients and practitioners. Assets are tangible or in-
tangible properties that participants can own, such as
health records.
Transactions are abstract actions and trigger a
chaincode to modify the ledger. Chaincodes (or smart
contracts) are a set of procedures defined by the
blockchain network designer to process inputs and al-
ter the resources. Examples of transactions are trans-
ferring a patient to another organization or granting
permissions. Access control lists are a set of rules
that can be defined to control access to different oper-
ations on resources.
All permission managements are handled through
chaincodes and access control lists and are enforced
by all participating nodes in the network.
ICT4AWE 2020 - 6th International Conference on Information and Communication Technologies for Ageing Well and e-Health
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