Page 79 - U4SSC Blockchain for smart sustainable cities

(2) Agility of the system
The agility of the system and the need to integrate the blockchain applications with other systems in the
future seems to be less important. Only 23 per cent of the use-cases emphasized its importance. It is
unlikely that complete historical data from legacy systems will be taken and entered into the blockchain,
particularly if it is a significant amount of data. Particularly, considering that any data are tamper-proofed
once in a blockchain, and that data are still vulnerable to common IT risks while outside the blockchain.
The transition of data between different systems needs to happen in the most controlled manner, given the
unique IT environment of each case. Experts and researchers in the blockchain system are already looking
into this issue and proposing solutions such as Cosmos, an ecosystem of blockchain applications that can
scale and interoperate with each other using a new consensus mechanism considered as Blockchain 3.0,
after Bitcoin and Ethereum. 107

(3) Blockchain solutions

Security is extremely important for all the use-cases. It constitutes one of the main concerns impacting
the legitimacy of the use of blockchain technology tremendously. In this context, most of the interviewees
presented blockchain as a secure option. Blockchain is often adopted because of its security properties,
particularly in the case of public blockchain. However, 70 per cent of the cases opt for a private distributed
ledger and permissioned blockchain mainly based on Ethereum and Hyperledger (e.g. Hyperledger Fabric
and private forks of Ethereum), where only authorized parties can access the data. Moreover, the consensus
mechanism differs from one case to another (proof of authority, proof of stake, proof of concept) but the
majority (70%) of the cases have not yet reached this stage.

(4) Scalability

Scalability refers to the ability of the system to sustain performance while growing and expanding, such
as increasing the number of users, storage requirements, and the response time per transaction as
the network grows. The number of users varies greatly from one use-case to another depending on
the progression in the development, and the targeted number of users as well. In some cases, such as
Digital Democracy, there are 60 000 users; while in other cases there are only 33 users. The scalability
constitutes one of the main challenging components regarding blockchain adoption. However, it is also
considered as a temporary technical issue that might be resolved by further research and development,
as new protocols evolve.

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