Page 98 - Handbook of Deep Learning in Biomedical Engineering Techniques and Applications

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

User Block - set of
Validation Add block to
Transaction transactions by miner the chain
Figure 4.1 Working of blockchain.

Application Layer
Data Ledger Layer

Consensus Layer

P2P network Layer

Figure 4.2 High-level architecture.

(iv) The miner then adds the block to the existing BC.
(v) Smart contracts are executed if required to complete the
transactions.
BC technology has evolved over three generations. BC 1.0
covers the applications that enables digital cryptocurrency trans-
actions. BC 2.0 introduces smart contracts and a set of applica-
tions beyond cryptocurrency transactions. BC 3.0 uses
decentralized application development to improve on the
scalability and throughput of BC 2.0 [3]. Characteristics of a BC
include security, immutability, provenance, decentralization,
anonymity, and transparency. These characteristics are achieved
using the digital infrastructure (Fig. 4.2) consisting of the following
layers [4,5]:
(a) Data ledger layer: This layer maintains a shared ledger that
contains distributed transaction records shared by all the
nodes in the BC network. This decentralization is a major
feature of BCs. Transactions can be added by any user anon-
ymously in the network. A transaction is the smallest building
block of a BC system. A set of transactions is maintained in a
block. The block is distributed to all the nodes in the network.
The node is a specific computer in the network. Each node
maintains a copy of the whole BC ledger. These blocks are
verified by specific nodes called as miners. Miners attach
the blocks to the BC that maintains blocks in a specific order.
This ledger is thus maintained as a linked list of blocks that
contain transactions.
Blocks in the chain are linked using their hash values. A one-
way hash function maps a data of arbitrary size to a fixed-size