Page 22 - U4SSC Blockchain for smart sustainable cities

Four blockchain architecture options are based on the type of ownership of the data infrastructure,
public or private and the level of “read, write and commit” permission granted to the participants
of the networks. These options are often presented (with the technological development) as new
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hybrid blockchains that combine different aspects of the technology. The following Table provides the
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explanation and a representation, as well as examples of blockchain for each architecture type.

Table 2: Examples of blockchain types

Blockchain Type Description Visualization Examples

Public permissionless This blockchain type is open to Bitcoin
blockchains everyone worldwide with an Internet Litecoin
connection to participate in the
blockchain consensus mechanism, Ethereum
to transact and observe the full
transaction log

Public permissioned This blockchain allows everyone Ripple
blockchain with an Internet connection to see
the transaction log, however, only Private version pf
Ethereum
a restricted number of participants
can contribute to the consensus
mechanisms

Private permissioned These blockchain systems restrict Rubix
blockchain the ability to transact and view Hyperledger
the transaction log to only the
participating nodes in the system.
The architect (or owner) of the
blockchain is able to determine who
can contribute to the blockchain
system and which nodes can
participate in the consensus
mechanisms
Private Permissionless These blockchain systems are Exonum (Partially)
Blockchain restricted in terms of who can
transact and see the transaction log,
although the consensus mechanism
is open to anyone

The type of blockchain adopted differs from one sector to another sector. The public sector requires
an in-depth analysis of what type of blockchain is the most adequate because as presented earlier,
all the blockchain types have their benefits and trade-offs for every type. The decision on the type of
blockchain technology adopted has an effect on the control, security, data ownership, and privacy and
access. The government must take into consideration serious privacy issues that the type of blockchain
involves in terms of sharing and storing sensitive data (personal, health, etc.).

12 U4SSC: Blockchain for smart sustainable cities