2.1.1 Scalability
Scalability is one of the most important aspects of
blockchains and can be motivated by the speed at
which participants of a peer-to-peer network can
reach consensus on the state of the blockchain (Hafid
et al., 2020). Mathematically it can be represented as
the maximum block size divided by the block inter-
val (Croman et al., 2016). Solving the scalability is-
sue can be done by either increasing the block size or
decreasing the block interval. However, external fac-
tors such as computing power, bandwidth, and storage
space (Buterin, 2021) call for an internal solution to
the problem. This is where the blockchain trilemma
arises, existing solutions such as the Proof-of-Stake
(PoS) consensus protocol give up decentralization in
favor of scalability. Using only a limited number of
validators, a particular type of node allowed to cre-
ate and confirm new blocks, PoS protocols can de-
crease network communication and increase scalabil-
ity. However, Proof-of-Work (PoW) protocols do not
differentiate between different types of nodes, and ev-
eryone has the same rights.
A low transaction rate leads to a problem where
transactions can no longer be processed immediately.
Therefore, scalability refers to the ability to support
high transactional throughput while maintaining per-
formance. Croman et al. (Croman et al., 2016)
identified some key metrics to measure scalability of
blockchain platforms, such as maximum throughput,
latency, bootstrap time, and cost per confirmed trans-
action, where the first two measurements are the most
important for a user who intends to use a blockchain
without being a miner or a validator.
Maximum throughput refers to the above-
explained concept of transactions per second. La-
tency is the time it takes for a blockchain to create
a new block, append it to the blockchain, and regard
it as confirmed. It can be divided into two parts which
are the block time and the time to finality. The for-
mer refers to the time needed to create a block and
add it to the blockchain. In contrast, time to final-
ity can be once again subdivided into deterministic
and probabilistic. Deterministic means that a block is
considered final once it is appended to the blockchain.
In other words, the block is no longer changeable
once it has been published. Probabilistic refers to the
blockchains in which a block is still subject to change
once it has been added to the blockchain, i.e., due to
the network not having reached consensus on the fu-
ture state of the blockchain. Bootstrap time refers to
the time it takes to download a blockchain and con-
firm all the blocks and transactions. Costs per transac-
tion are external factors such as setup cost, hardware
cost, storage cost, and power usage.
2.1.2 Decentralisation
Decentralisation is at the core of blockchain tech-
nology, but also a bottleneck regarding scalability
and security. It describes the transfer of control and
decision-making rights from a central authority to
a distributed network. A characteristic of decen-
tralisation in blockchains is the distrust between its
participants, which is desired and required for it to
work correctly. Measuring decentralisation depends
on the type of blockchain. Generally, two types of
blockchains exist or rather two types on how de-
centralisation must be measured. One type uses the
Proof-of-Work consensus protocol, while the other
type uses Proof-of-Stake or a similar consensus pro-
tocol where the rights to create a new block are given
to the node based on staked capital (Conway, 2022b).
The decentralisation (and security) of a Proof-of-
Work blockchain depends on the network’s hash rate
and how distributed it is. A network’s hash rate is the
cumulative hash rate of all the (mining) nodes par-
ticipating in the block creation competition. There-
fore, the higher the network’s hash rate, the harder it
is to disrupt it (Conway, 2022a). Decentralisation of
a Proof-of-Stake or similar blockchain can be mea-
sured in the number of validators, the distribution of
staked capital among the validators, and the percent-
age of token supply that has been staked (Conway,
2022a). Another metric is the Initial Token Alloca-
tion. It can create unfair advantages for a group that
receives many tokens and determine the next block
and chain governance.
For Proof-of-Work and Proof-of-Stake, it is im-
portant to measure how many nodes or pools (a pool is
a group of miners which join together to increase their
chance of creating the next block) control the major-
ity of the network. The NC is defined as the mini-
mum number of nodes required to get 51% of the to-
tal capacity (either in computing power or staked cap-
ital) (Srinivasan, 2017).However, for networks with a
lower Byzantine Fault Tolerance (BFT), it is only re-
quired to control one-third of the network’s comput-
ing power or staked capital.
2.1.3 Security
In cybersecurity, the CIA acronym stands for con-
fidentiality, integrity, and availability. Confidential-
ity involves the tasks of keeping particular informa-
tion secret. This is done in blockchain platforms in
the form of encrypted addresses. Users can interact
with the system using public key hashes without re-
vealing their real identity. However, this only guar-
antees pseudonymity as the ledgers are public and
transactions can be traced. Once a public address is
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