Page 105 - Handbook of Deep Learning in Biomedical Engineering Techniques and Applications

Chapter 4 A critical review on using blockchain technology in education domain 93

appended with document hash. This ensures anonymity, pri-
vacy, integrity, and decentralization. Dragon chain follows
this consensus approach.
(d) Proof of believability (PoBi): Smaller blocks deliver better
throughput but can be compromised easily. To overcome this
trade-off between performance and security, PoBi uses an
intrashard believable first approach. Here, validates are cate-
gorized into believable and normal groups. Based on the
reputation of a node (token balance, community work, repu-
tation), a believability score is calculated. There may be one
believable validator per group, who validates the committed
transactions. This is done quickly (with low latency) but
compromises on security. To overcome this security lapse, a
set of normal validators can sample these transactions and
verify them. If inconsistency is detected, then believable
validators are penalized by forfeiting the coins they hold.
This will prevent the believable validators from misbehaving.
Hence, this approach achieves low latency and is also secure.
IOSTChain uses this consensus mechanism.
(e) Proof of stake (PoS): In PoS, miners can validate block in
proportion to the number of coins they possess. A node can
join the network only if the wallet contains a basic minimum
number of coins. Miners need to deposit (stake) a percentage
of their coins. Nodes in the network then vote for the valida-
tors among the miners. In case of false validation of transac-
tions, the amount staked by the miners will be forfeited. The
miner receives a transaction fees for mining. PoS follows an
internally game theoretic approach. Hence, all the validators
should be identifiable; hence, an authentication procedure
is essential for validators since malicious acts should be
prevented. Ethereum, Startis, and Navcoin are based on PoS.
This approach is less prone to 51% attack [8] and is more
decentralized. It is also energy efficient as no complex computa-
tions are involved. The major issue is that there is a possibility
of power concentration among some miners.
(f) Delegated proof of stake (dPoS): Like PoS, nodes (delegates)
stake their coins in this consensus protocol. These delegates
then appoint witnesses by voting. These witnesses perform
validation. In dPoS [8], witnesses gain reputation when they
gain more votes from the delegates. Lisk uses DPoS. This
method is fast. It is semicentralized but is scalable and less
resource intensive. It is secure against 51% attack.
(g) Leased proof of stake (lPoS): In PoS, delegates/nodes should
possess a minimum number of coins to participate in the
network. This reduces the chances of smallholders from