Page 100 - Handbook of Deep Learning in Biomedical Engineering Techniques and Applications

88 Chapter 4 A critical review on using blockchain technology in education domain

(b) Consensus layer: Users of the network must prove themselves
as legitimate users. As a result, reaching a consensus agree-
ment is one of the key features of a distributed technology.
Consensus ensures that the ledger is unchangeable, immu-
table, and shared throughout its life. After agreement on the
consensus mechanism, the peers execute the consensus
protocol to validate transactions and create blocks and hashes.
New transactions recorded on the ledger are validated by
miners. The process for selecting the actual node that will
add the next block among all the miners is referred as a
consensus protocol. This is done conventionally by solving a
complex cryptographic puzzle. This process enables random
selection of miners and prevents adversary nodes from adding
fraudulent blocks in the BC network. In public BCs, successful
miners are rewarded. Privacy of data is achieved using crypto-
graphic encryption of data and ensuring that transactions are
authenticated and verified. It is a crucial part of BC technology
that ensures hardening security to avoid network breaches.
(c) P2P network layer: Physically the BC data structure exists
over a peer-to-peer (P2P) network that links its members.
While BCs are based on P2P systems with decentralized
control, conventional databases are based on clienteserver
architecture with centralized control. Hence, BCs are more
scalable. This network connects various physical devices
including user nodes, validation servers, and node servers.
(d) Application layer: Various applications including manage-
ment of assets, certificates, banking transactions, land registra-
tions using the underlying BC technology can be implemented
and deployed in this layer. It contains application logic imple-
mented using smart contracts. It is collectively controlled by
the participants who deploy the code onto the BC network
when it is operational. Any participant holding access and
control of the deployed code can write the application layer.
Smart contracts are business agreements embedded into the
transaction database (ledger) that are executed automatically
with the transactions. Contracts consist of rules that define the
flow of values and the state of transactions. The contract is smart
because it is a computerized protocol that executes the terms of
the contract to ensure a successful transaction. Smart contracts
are intended to guarantee one party that the other will satisfy
their promise. To codify business contracts in BC, smart contracts
must be transparent as the participants should be able to prove
each other’s actions pertaining to the contract. This is essential
to verify whether a contract has been successfully completed or
has been breached.