IEEE Systems, Man and Cybernetics Magazine - October 2022 - 13

◆ No data provenance: This is also obvious since data
provenance relies on data immutability.
◆ No transparency: Transparency in a public blockchain
is established by making the entire blockchain accessible
and guaranteeing that all records have not been
tampered with and never will be. Even if a permissioned
blockchain is not encrypted and publicly accessible,
the lack of data immutability destroys the
foundation of transparency.
◆ No privacy: Because a user needs to be granted permission
to join and stay in a permissioned blockchain,
his or her identity cannot be protected, at least not at
the same level offered by a public blockchain.
◆ No trust: Data immutability is one of the most fundamental
pillars for establishing trust. Without it, the integrity
of a system's operation will be called into question.
◆ No security: The inability to ensure data immutability
means that the owner of a permissioned blockchain
could allow favored users to double spend. According
to our definition of security for blockchain operations,
this would be a serious breach.
◆ Fault tolerance and atomic contract execution: Blockchain
technology created a completely new way of
constructing robust fault-tolerant systems. In the context
of crash fault tolerance, the process of randomly
selecting a single node to assemble the block, and in
the case of smart contracts, using the same single node
to execute the smart contract code,
still works well even if the nodes are
centrally controlled by an individual
or organization. However, to tolerate
malicious faults (i.e., Byzantine
faults), decentralization is indispensable
to fault tolerance mechanisms.
Without decentralization, fault tolerance
mechanisms in a permissioned
blockchain would suffer from the
same problem faced by all traditional
Byzantine fault tolerance solutions.
To be able to tolerate malicious faults,
we must assume that all replicas fail
independently. However, such an assumption
is hardly valid in a permissioned
blockchain because all the nodes are controlled
by the owner. How can we be sure
the owner is not malicious? The whole
point of blockchain technology is decentralization
so that we do not have to trust
an individual or organization. That being
said, all traditional Byzantine fault tolerance
solutions are essentially permissioned
systems because of the need to
establish known membership. That is
why we list fault tolerance and atomic
contract execution as the remaining benefits
of permissioned blockchains.
Future Research Directions
Research on blockchain is highly active due to plentiful
opportunities. Here, we mention three directions of active
research and development: 1) increasing the effective
throughput of blockchain, 2) reducing the electricity cost of
achieving consensus in blockchain, and 3) increasing the
anonymity of blockchain. In the first direction, a general
approach is to utilize off-chain and multichain channels.
The most well-known development is perhaps the payment
channel proposed by the Lightening Network [6]. In the second
direction, proof of stake has been intensively studied,
and various algorithms have been proposed [21], [22]. Traditional
consensus algorithms, such as Practical Byzantine
Fault Tolerance, have also been proposed to address energy
consumption. However, we strongly oppose such an
approach because it is directly against the decentralization
principle of blockchain technology. In the third direction,
there have been efforts to improve the pseudoanonymity
provided by blockchain technology such that transactions
cannot be easily linked. The basic idea is to remove singletransaction-level
linkability to mix a group of transactions
together, which is referred to as CoinJoin [23]. The scheme
can be further improved via blind signatures [24].
Conclusion
In this article, we strived to give a precise description of
blockchain technology, including its design principle,
Trust
Data
Immutability
Data
Provenance
Centralized Control
Cryptography
Consensus
Privacy
Blockchain
(Smart
Contract)
Security
Atomic
Contract
Execution
Transparency
Fault
Tolerance
Censorship
Resistance
Figure 2. The analysis of blockchain technology in the context of
centralized control.
October 2022 IEEE SYSTEMS, MAN, & CYBERNETICS MAGAZINE 13
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