Page 106 - Handbook of Deep Learning in Biomedical Engineering Techniques and Applications

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

joining the network. This also reduces transparency in the
BC. In lPoS, smallholders can lease their coins to the network
and get benefitted. Waves uses lPoS.
(h) Proof of importance (PoI): It is a modified version of PoS that
favors wealthy miners. It is based on the concept of vesting or
harvesting a node. A minimum of 10,000 coins are required
for a node to be harvested. In return for the harvesting, the
node receives the transaction fees that the validator collects
as the reward. PoI score depends on the harvested amount,
which inturn improves the chances of adding the node to
the network. This protocol was initiated by the New Economy
Movement (NEM) cryptocurrency. The major advantage is
that it has high throughput and low latency. It consumes
only low computational power and network overhead. The
disadvantage of PoI is that it requires the large number of
transactions. It is favorable for the IoT applications.
(i) Proof of authority (PoA): In PoA, only selected authorities
(called validators) elected by delegate nodes produce new
blocks. This can be done only when a majority consensus is
reached. This is similar to dPoS. The validators identity are
at stake as they are made public. Thus, the threat of their
identity being ruined incentivizes them to act in the best
interest of the network. By identifying the validators, PoA
becomes semicentralized and is more suited for private/con-
sortium BC.
(j) Proof of weight: PoS is bit biased as it favors wealthy miners
with more coins. To overcome this disadvantage, PoWeight
considers other weighted factors such as reputation, space,
time, IPFS data, and soon. The fundamental advantage of
this system is customization and scalability. Incentivizing is
a big challenge for this consensus algorithm.
(k) Proof of stake and velocity (PoSV): Linear coin-aging function
in PoS results in high incentives for hoarding and less
incentives for staying online. PoSV is designed to encourage
both ownership (stake) and activity (velocity). Velocity is
calculated based on the ratio of coins used to total number.
Velocity increases as more coins are in circulation. Hence,
hoarding is prevented using exponential decay function, as
new coins accumulate at a faster rate than stale ones and it
changes the stakeholder’s incentives. This reduces 51%
attacks in PoS. Reddcoin uses PoSV consensus.
(l) Round robin consensus model: Nodes that are available take
turns in mining the blocks in the private BC. There is no need
to solve a cryptographics puzzle, and it is energy efficient.