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STS1080 Asma A. et al.
Ethereum, it uses the same algorithm for consensus (proof of work) as bitcoin
which is extremely costly and energy inefficient. Personal data will be stored
off chain so records cannot be determining whether the record is legitimate.
So, authentication is legitimate, but the data may not be accurate.

2. Methodology
In this section, we will first present an overview of Blockchain, and its
different platforms. We will then provide the different evaluation scenarios we
have run on a selected blockchain platform. Each scenario presents a pseudo-
function of a healthcare application and has different users and purposes.

1.3. Overview of Blockchain
Blockchain is a distributed ledger system which allows multiple users to
securely store and share data. It gets its name from that fact that transactions
are stored in blocks which are linked with each other to form a chain. A block
contains various information about a transaction, including the time of the
transaction; the sequences of transactions; and a pointer to the previous
transaction (Hash value of the previous block). Indeed, linking transaction
blocks using the hash will ensure the integrity of data on each transaction
(previous block can’t be altered), and prevent from inserting new blocks in-
between 2 pre-existing blocks. In addition, to ensure full data integrity and
availability in the blockchain, each blockchain platform guarantee the key
blockchain concepts: Data immutability, Shared ledger, consensus,
Permissions and data encryption.. Given that, there are two different types of
blockchains which have significant distinctions: Public and Private. Public
blockchains are the purest form of blockchain which allows any user to join
the blockchain and does not discriminate between users (Smith T. D., 2018).
However, private blockchains seem to be used more in the industry as there
are more security and privacy constraints, and users need to request
permission before becoming a member of the blockchain. Members of a
private blockchain can be further restricted with different access privileges.
The main advantage of a public blockchain is its autonomy. All users have
similar privileges, and no party can control stored data, which means that users
don’t have to trust and rely on a third party. However, public blockchains are
extremely large and consume a large amount of energy as no user is restricted
access. On the other hand, private Blockchains tend to be smaller and flexible
as only limited number of users are allowed access, and they have different
permissions and access privileges.

1.4. Evaluation methodology
In this study, we have used Hyperledger fabric for feasibility on healthcare
applications. Hyperledger fabric has been selected due to various factors,
including the use of a strong hashing algorithm like SHA-2, and providing

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