[Building Research & Information vol. 49 iss. 1] Fu, Yonggui Zhu, Jianming - Trusted data infrastructure for smart cities a blockchain perspective (2020) [10.1080 09613218.2020.1784703] - libgen.li

Building Research & Information
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/rbri20
Trusted data infrastructure for smart cities: a
blockchain perspective
Yonggui Fu & Jianming Zhu
To cite this article: Yonggui Fu & Jianming Zhu (2020): Trusted data infrastructure for smart cities:
a blockchain perspective, Building Research & Information, DOI: 10.1080/09613218.2020.1784703
To link to this article: https://doi.org/10.1080/09613218.2020.1784703
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BUILDING RESEARCH & INFORMATION
https://doi.org/10.1080/09613218.2020.1784703
Trusted data infrastructure for smart cities: a blockchain perspective
Yonggui Fua and Jianming Zhub
a
School of Information, Shanxi University of Finance and Economics, Taiyuan, People’s Republic of China; bSchool of Information, Central
University of Finance and Economics, Beijing, People’s Republic of China
ABSTRACT
ARTICLE HISTORY
It is very important to improve the operation and management efficiency of data and network for
the construction of smart cities. The current trust infrastructure in smart cities shows obvious
shortcomings, accordingly, this paper proposed the idea of applying blockchain to smart city
systems and as their trust infrastructure. The research method is: firstly, the network architecture
and data architecture of smart cities were proposed, and the database was classified as a shared
database, authorized access database or private database. Secondly, the overall architecture
model of the blockchain in a smart city system was constructed, and the blockchain was
classified as a public blockchain, consortium blockchain or private blockchain. Thirdly, the
realization principle of the cross-blockchain interoperability of different blockchains, the
construction principle of dynamic smart blockchains, and the selection method of blockchain
authentication nodes were designed, and the supervision method and supervision content of
blockchain system operation were discussed. The research result is: took the smart
transportation subsystem as an object, through algorithms, the operation principle of the
blockchain was constructed. This research can provide a reference for the construction of trust
infrastructure in smart cities and can promote the application research progress of blockchain
technology.
Received 9 February 2020
Accepted 14 June 2020
Introduction
The extensive application of cloud computing, Internet
of Things (IoT), artificial intelligence and blockchain,
etc. information technology, has promoted the data
exchange and business integration among different
industries, and accelerated the realization progress of
smart network. The operation of smart cities is inseparable from the support of mobile Internet technology, IoT
technology, communication technology and data management technology. A smart city is an information ecological mode as different institutions and industrial
systems integrating highly and operating automatically,
and is also the ultimate vision of future urban
development.
The idea of a smart city originated from the concept of
smart earth proposed by IBM in 2008 (IBM, n.d.). After
more than ten years of development, smart cities have
become an important goal of urban construction in
some developed countries. The United States and the
European Union are making great efforts to build their
own smart cities. The ranking result of the ‘IESE urban
dynamic index’ in 2018 showed that the best smart cities
in the world were New York, London, and Paris (HWW,
2018). In China, the national government put forward
CONTACT Yonggui Fu
[email protected]
© 2020 Informa UK Limited, trading as Taylor & Francis Group
KEYWORDS
Smart city; blockchain; trust
infrastructure; database
guidance for the construction of smart cities, and it
was proposed to build a batch of smart cities with distinctive Chinese characteristics in 2020 (NDRC of
China etc., 2014). The construction of smart cities has
become an important indicator for measuring the level
of informatization and industrialization of a city.
Smart cities involve all aspects of urban operation,
such as government agency operation systems, urban
transportation systems, medical and health systems, education and scientific research systems, culture and tourism systems, industrial control systems, and agricultural
automation systems, etc. In smart cities, data smart
transmission and business cross-control are realized
among different institutions and industrial systems.
These different operation systems dynamically integrate
and adjust the data transmission according to the
business operation requirements, improve the efficiency
of urban operation, and promote people’s living level
and living quality. The operational basis of smart cities
is data sharing, and smart analysis and decision-making
of data. At present, to a certain extent, many fields of
some cities with developed information technologies
and economic living levels have already realized smart
management and operation, such as smart traffic light
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Y. FU AND J. ZHU
systems, smart industry control systems, smart agriculture greenhouse temperature and humidity control systems, and smart home systems, etc. However, the
overall development of smart cities is still in its initial
stage, which is mainly reflected in the fact that different
smart systems are independent of each other, information and data cannot be well transmitted in a dynamic
and real-time way through the network, and the
cooperation degree among businesses is not enough.
The reasons for this situation include the uneven functional level of the hardware services of the smart systems
in different fields, and the large differences in the software environment, as a result, which lead to the cost of
data transmission being very high. The reasons for this
situation also include the requirement as data confidentiality, and the security and credibility of data transmission among different application areas cannot
obtain enough guarantee, as a result, which restrict the
data transmission and business collaboration in different
business fields. For the construction of the hardware
environment, the government departments of cities can
uniformly coordinate and solve according to requirements. For the matching problem of the software
environment, the government departments of cities can
build information transmission interfaces for different
application software to achieve it. For the security and
credibility problem of data transmission, when building
a smart city system, the following problems must be
solved:
(1) The security problem of data transmission among
different application areas. Data transmission is
the basic guarantee for ensuring the operation of
smart city systems. The data content and structure
mode of different industries are different, due to
the complexity of smart city network architecture
and industrial contents, the security risks of data
transmission are also diversified. At present, the
security problems of data transmission among
different industries are very prominent, which are
also the important problems that affect the
cooperation among different systems of smart
cities.
(2) Reliability problem of transmitted data among
different application areas. Different application
fields of smart cities are relatively independent systems, due to their private interests, it is difficult to
fully guarantee the authenticity and reliability of
the transmitted data of these relatively independent
systems. How to identify the authenticity and
reliability of the data source and data content
when the data are received, is a key problem of
determining the operation efficiency of smart cities.
(3) Privacy and confidentiality problems of data among
different application areas. In the process of data
transmission, different systems of smart cities need
to ensure their data are only transmitted to the
determinant receivers, and the unauthorized privacy
and confidential data can be protected and are not
illegally accessed.
(4) Traceability problem of the sources of input and
output data in different application fields. A smart
city is an automatic operation system, and is a
mutual cooperation system of different application
subsystems and perception subsystems. Due to less
human participation, it is necessary to record the
source and destination of data, to ensure the disseminators and receivers in the data transmission process are traceable.
(5) The supervision problem of data operation and data
change. In the smart city system, although it is
difficult to realize the smartness of all the data dissemination and urban management, but the completed smart system is also very complex. The
complexity includes not only the complexity of
business content, includes the complexity of
business cooperation, but also includes the complexity of data transmission. Therefore, under the current informatization level, it is unrealistic for a
fully automated smart city operation system that is
separated from supervision. If the data operation
lacks supervision, then the smart city operation
will be out of control, once there is a problem in a
certain operation section, the information management system of the whole city will produce continuously wrong operation results, which will ultimately
result in urban management confusion.
Therefore, building a fully connected data trust guarantee system is the basis for the effective operation of
smart cities. At present, in the field of information and
network application systems, the related research results
mainly used information security technologies or humanistic regulation management to solve its trust guarantee,
therein, the information security technologies include
identity authentication technology, firewall technology,
etc., such as.
Wu et al. (2018) proposed a method of identity
authentication based on the motion data and physiological data generated by wearable devices. Ikarashi et al.
(2018) designed a proactive firewall system based on
software-defined network and realized it. Fu and Xu
(2011) researched network trust from the perspective
of game theory. Due to the lack of supervision on the
operation of the application system and the responsibility traceability on data access, these methods cannot
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completely solve the problem of trust guarantee of the
application system. Similarly, as a product of information ecology, the current trust guarantee system proposed in the application research of smart cities also has
the same deficiencies as other application fields.
Trusted data refer to the process of the generation,
change, dissemination and storage of data are traceable,
the data have not been maliciously damaged, changed or
leaked in the process of operation, and the authenticity of
the data can be proven. For trusted data, the business
content and business subjects are recorded, which are
undeniable. The characteristics of blockchain (Nakamoto, 2008; Wood, 2014) can solve the problem of security and credibility, and provide consistent transmission
and management protocols for data in different application fields. The blockchain-based network is a real
trustworthy value network, and is a reliable bridge for
communication and coordination in different fields of
the city. Therefore, this paper proposes to build a trust
guarantee system in the smart city, and which makes
blockchain as data trust infrastructure. Due to the complexity of the structure of smart cities, this paper proposes to build different blockchain systems for different
industrial fields, and in the same industrial field, different
blockchain systems are built according to the characteristics and uses of data, through protocol the entitled
mutually accessible blockchain systems access each
other and realize the strengthen authentication. The
functional structure and implementation mode of the
blockchain are dynamically adjusted according to the
smart requirements of the smart city, to fulfil the smart
task. The regulators complete the supervision to the
blockchain operation system and the business operation
process in different industrial fields. Thus, the blockchain
system can ensure the credibility of the operation data of
smart cities, and can promote the integration of different
industrial fields of smart cities and the realization of
business intelligence.
The research objectives in this paper are to combine
the network architecture and data architecture of smart
cities, design the application architecture mode of
smart cities based on blockchain, and use the technical
characteristics of blockchain to realize the data trust
guarantee of smart cities. The contributions of this
paper are as follows:
(1) The shortcomings of the existing trust guarantee of
smart cities were analysed, and the significance of
the trust guarantee of smart cities based on blockchain was discussed.
(2) Combining the network architecture and data architecture, the architecture of a smart city based on
blockchain was constructed.
3
(3) The principle of interoperability between blockchain, the construction method of dynamic blockchain, the selection method of consensus
authentication nodes were designed, and the smartness of blockchain was realized.
(4) The status of the blockchain supervision system was
discussed, and its supervision functions were
designed.
(5) The operation principle of the blockchain system of
a smart city was analysed through instance
algorithms.
Related works
Blockchain and its application
The generation and work principle of blockchain is: The
sender digitally signs the data → the signature data are
broadcast in the blockchain network → the receivers
consensus authenticate (verify the authenticity of the
data and confirm the identity of the sender) → the receivers build the blockchain respectively → the blockchain
and the received data are distributed stored by the receivers (the blockchain and the received data can be stored
together or separately). For the structure and work principle of blockchain, there have been many discussions
and analysis results in academic circles, such as references (Cai et al., 2019; Papakostas et al., 2019). So, in
here, no more details will be provided.
As a comprehensive technology system and trust
infrastructure system, blockchain has become the concerned focus of most countries in the world, such as
the United States, the United Kingdom, China, Australia,
the European Union, Japan, South Korea, etc. (CAOIC,
2019), the concerned focus on blockchain from these
countries includes the formulation of policies and development strategies, supervision measures, technology
innovation and product research and development, standard formulation, etc., and the involved fields include
finance, logistics, energy, government affairs, IoT, etc.
After ten years of development, blockchain has gradually
been recognized and applied.
The research progress on blockchain
By comprehensively analysing the research results of
blockchain in academia, the results can be divided into
three categories: blockchain characteristics and its application value analysis, blockchain technology and working methods research, and blockchain application
architecture design.
(1) Blockchain characteristics and its application value
analysis
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Y. FU AND J. ZHU
For instance, Chen (2018) analysed the value of blockchain applying in library smart service. Kim and Shin
(2019) used a structural equation model to research the
influences of blockchain technology characteristics to
supply chain partnerships. Khatoon et al. (2019)
researched the benefits of blockchain applying in the
field of energy efficiency. Zhang et al. (2016) analysed
the influence of blockchain technology to government
governance innovation. Di Silvestre et al. (2020) analysed
the perspective of blockchain applying in power systems.
These are the elementary results of blockchain
research, and the content is relatively simple, which
mainly promote the understanding of blockchain itself
and the analysis of the application value of blockchain.
(2) Blockchain technology and working methods
research
For instance, Singh et al. (2020) analysed the influence
of the current side-chain technologies and the limitations
of its application, and proposed corresponding suggestions. Li et al. (2019) combined blockchain technology
and searchable symmetric encryption to provide secret
protection and proof of completeness for data. Zhang,
Cui, Ma, et al. (2019) proposed a crowdsourcing scheme
based on blockchain technology. Kim et al. (2019) proposed a blockchain-based electric vehicle safe charging
system. Cai et al. (2020) proposed a consensus algorithm
based on dynamic reputation for energy blockchain.
These results mainly introduced the design or working method of some a technology application of blockchain, and these research results are helpful to the
construction of blockchain in specific application fields.
(3) Blockchain application architecture design
For instance, Ren (2018) proposed the architecture
model of blockchain applying in tax administration
business. Zhang, Cui, Zheng, et al. (2019) proposed a
scheme for blockchain applying in the access control of
electronic medical record. Che et al. (2019) proposed a
consortium blockchain-based framework for the transaction authentication of renewable energy. Fan et al.
(2019) proposed the structure for improved PBFT consensus algorithm-based dual blockchain base station
dynamic loop monitoring system.
These results are mainly the architecture design of
blockchain applied in specific fields, which provided targeted schemes for specific application environment.
These research results provided guidance for the research
and development of blockchain products and the construction of application systems, which belonged to the
forefront of blockchain research at present.
Classical research on the system construction of
smart cities
At present, research on the construction of smart cities is
still in its primary stage, the corresponding research
results are few, and mainly focus on discussion and
analysis. Such as, Wang et al. (2012) analysed the supporting role of information service platform on the
development of a smart city, and constructed the corresponding framework model. Wang et al. (2018) proposed to build the guarantee system of a smart city
from current information security technology. Li et al.
(2018) evaluated the construction level of a smart city
by constructing index system and model. Jiang (2020)
proposed to apply cloud computing technology and
IoT technology to smart cities, for resolving the information sharing between different information systems.
At present, few classical research results are on the
trust guarantee of data in smart city systems, and a few
researches on the information security of smart cities
mainly focused on the applications of mature information security technologies in smart city systems.
Research on blockchain applications in the
construction of smart city systems
At present, some scholars have already begun to pay
attention to the application research of blockchain in
the field of smart cities, and have obtained some results,
such as: Yu et al. (2019) proposed a scheme of applying
blockchain to the audit of big data that generated in a
smart city. Gong et al. (2019) proposed a framework
for blockchain applying in device management of IoT
in a smart city. Wang (2018) analysed the value of blockchain applying in smart city big data platforms. However, after analysis, it is found that the current research
on the application of blockchain in smart cities are still
in the exploration stage, and have not formed a valuable
blockchain application architecture for smart city trust
guarantee. The researchers have not looked up the
research results that combined blockchain interconnection and blockchain supervision to solve smart city
trust guarantee. Therefore, the research in this paper is
realistic and instructive.
Materials and methods
The key problems of smart cities are network construction and technology application, only realizing the digitalization of urban construction can further build smart
cities. In the smart city system, different subsystems take
the network as the platform to integrate, and cooperate
with each other to become a whole. In this large macro
BUILDING RESEARCH & INFORMATION
system, data generation, data circulation, data analysis,
data application, etc. become the core and support of
city operations. Network security and network trust are
the basis of network operation and development. For
smart cities, information interaction and business
cooperation are the main contents, so network security
and network trust are essential for the construction of
smart cities. Because smart cities embody the ultimate
goal of people-oriented and sustainable development,
so, only under supervision can the efficiency and quality
of smart city operation be ensured. Therefore, the network architecture system, data system, trust guarantee
system, and supervision system will become the important infrastructures of smart city applications. While
basing on the current blockchain technology and its
functional characteristics, blockchain technology will
become the fundamental technology to solve the
deficiency of the current trust guarantee system and
build a new trust guarantee infrastructure, and its value
and status are irreplaceable.
The network system of smart cities
The development of smart cities should reflect sustainability and strong compatibility, the function and
cooperation relationship of different subsystems should
be able to be adjusted according to actual requirements,
new systems should be able to be absorbed, and the
structure of existing systems should be able to be changed. Therefore, the network architecture of smart cities
should reflect the openness and accommodation, and
be able to flexibly upgrade the corresponding service
capabilities with the development of information technology. The network architecture of the smart city is
shown in Figure 1.
Figure 1 describes the abstract network architecture of
the smart city. In Figure 1, geographical information system, safety monitoring system, weather monitoring system, etc. are systems that based on the IoT, they are the
perception subsystems of the smart city. The perception
subsystems perceive the physical world through sensor
devices and produce information. According to the
characteristics and uses of information, part of the information of the perception subsystems are privately stored
by the systems, and part of the information of the perception subsystems are shared by application subsystems
of the smart city through the cloud service platform of
Internet (or metropolitan area network)(either fully
sharing or authorized sharing). Internet (or metropolitan
area network) is a public network that integrates different application subsystems (social economic systems),
perception subsystems, and undertakes data interaction,
data transmission, data analysis and processing. Usually,
5
through the cloud platform the smart city system satisfies
the data requirements from the application subsystems.
Smart transportation system, smart community service
system, smart medical system, smart energy system,
etc. are the application subsystems of the smart city,
the operation of these subsystems depend on the
decision information that generated from the analysis
on the data of the perception subsystems and application
subsystems.
The data system of smart cities
The data produced by the smart city network system are
the information environment on which the smart city
depends. In the process of operation, each application
subsystem collects the relevant data from the smart city
system according to the system business requirements.
The smart analysis and decision-making system of the
smart city analyses the relevant data to guide the operation of each application subsystem. Basing on the
above analysis, and referring to the structure in Figure
1, the data architecture of the smart city is shown in
Figure 2.
In Figure 2, the data bodies of each perception subsystem or application subsystem of the smart city are
divided into three categories: shared database, private
database and authorized access database. In Figure 2,
the shared database, private database and authorized
access database are just abstract concepts, and each category of database can be composed of several different
databases. The shared database is the data set used for
sharing in each subsystem, and these data will be provided by each subsystem and stored in the shared database platform of the smart city. The shared database is
accessed automatically and intelligently in the smart
city. The private database is the proprietary data set or
confidential data set owned by each subsystem. The
data of the authorized access database are the data that
can be accessed under the authorization of each subsystem, and these data are only shared under the authorization of specific application subsystem or perception
subsystem. It should be noted that the definitions of
shared database, private database, and authorized access
database are only used in this paper, which are different
from the definitions of shared database, private database,
and authorized access database in other application fields
or literatures. Shared data, private data, and authorized
access data can be produced by a subsystem running
independently, or produced by a subsystem cooperating
with other subsystems. When an application subsystem
has business requirements, the smart city will connect
with the relevant perception subsystems and application
subsystems according to the requirements, collect
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Y. FU AND J. ZHU
Figure 1. The network architecture of the smart city.
relevant data from the authorized access databases under
the authorization of the relevant systems, and then collect relevant data from the private databases of this application subsystem and the shared databases. These
relevant data are collected, integrated, and analysed,
finally formed the decision results, and the decision
results are transmitted to the application subsystem
with business requirements. In addition, a smart city is
not a closed system, because of the business requirements, sometimes, it is also necessary for collecting
data from Internet or other databases outside the city
system to support the business operation of the smart
city (In Figure 2, the smart transportation subsystem is
made as an example to describe the business and data
processing relationships. In fact, other subsystems
(such as smart energy system, smart community service
system, smart medical system, etc.) also have similar
business and data processing structures with smart transportation subsystem. To retain the simplicity and understandability of the picture, this paper does not draw.).
The operation of a smart city makes the data volume
grow rapidly (The data are produced by the system.), and
its data capacity will reach the level of big data.
Generally, the shared databases are stored in the cloud
service platform, due to the business requirements, the
data gathered by the application subsystem are integrated and analysed by the data processing organization
built by the smart city, and the corresponding results are
transmitted to the application subsystem for use. The
connections among an application subsystem and
other subsystems of the smart city, and the collections
to the authorized access databases are completed by
the cooperation among different subsystems.
The blockchain system of smart cities
Because the structure of each subsystem of a smart city
and its position in social and economic life are different,
the function and structure of data are also very different,
and each subsystem is a relatively independent economy,
so it is necessary to build different blockchain systems for
different types of data bodies, and different blockchains
with access rights can operate and record each other.
According to the characteristics and application scope
of blockchain, blockchain can be divided into public
blockchain, consortium blockchain, and private
BUILDING RESEARCH & INFORMATION
7
Figure 2. The data system architecture of the smart city.
blockchain. In this paper, different data bodies correspond to different business requirements, for the data
that produced by some an application subsystem (social
economic subsystem) or some a perception subsystem,
but they are used to be shared with other subsystems
under authorization (If the data are produced in the process of some a subsystem running independently, then
the subsystem independently owns the authorized
shared data. If the data are produced in the process of
some a subsystem cooperating with other subsystems,
then the subsystem and other business collaboration subsystems own the relevant authorized shared data
together.), the generation and change process of the
data bodies will be recorded through building the consortium blockchain. For the data produced by application subsystem or perception subsystem, but are
freely accessed by all subsystems of smart city through
the shared database platform, the generation and change
process of the data will be recorded through building the
public blockchain. For the data independently owned by
the application subsystem or the perception subsystem,
the private blockchain is built to record its generation
and change process. For the data collected from Internet
or other field databases outside the city, in the process of
the data being introduced into the application subsystem, the operation and change process of the data can
be recorded by the public blockchain, the consortium
blockchain, or the private blockchain according to the
characteristics of the data. It needs to be noted that the
definitions of the public blockchain, the consortium
blockchain, and the private blockchain proposed here
are only used in this paper, which are different from
the definitions of the public blockchain, the consortium
blockchain, and the private blockchain proposed in other
application fields or literatures. The data produced by a
business activity of smart city subsystem (application
subsystem or perception subsystem) may be stored in
shared database, authorized access database or private
database according to the requirements, that is, a
business activity of smart city subsystem may bring the
operation and data record of the public blockchain, the
consortium blockchain, or the private blockchain.
The interflow of each business system results in the
interaction among data of each business system, and
results in the interaction among records of different
blockchains. Therefore, it is necessary to build protocols
for data communication and blockchain records of smart
cities, so as to ensure that the operation of smart cities is
carried out in accordance with unified standards. In the
smart city system based on blockchain, the generation,
broadcasting, recording and storage of data are all completed by blockchain, and the generation, broadcasting
and recording of data are the basic work principle of
blockchain. To the work principle of blockchain, as
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Y. FU AND J. ZHU
discussed in section ‘Related works’ of this paper, many
results have already been produced. Before being introduced into the blockchain system, the security and privacy protection problem of the data is an important
content of data management, and there are many
research results at present, such as literatures (Chanson
et al., 2019; Feng et al., 2019; Ren et al., 2019; Xu & Li,
2019). The storage security problem of blockchain data
is also an important content of blockchain data management, and there are also many research results at present,
such as the literature (Fang & Peng, 2019; Li & Han,
2019). Therefore, for the problems of operation principle, blockchain data security and privacy protection,
and data storage security of the smart city blockchain
application system, this paper will not introduce them
in detail. In section ‘The blockchain system of smart
cities’ of this paper, from four aspects as the overall
architecture, cross-blockchain interoperability among
different blockchain, smart blockchain, and blockchain
supervision to introduce the construction problem of
blockchain system of the smart city. At present, there
is less research on cross-blockchain interoperability
among different blockchains, smart blockchains, and
blockchain supervision, and the implementation of corresponding results is not strong in reality. Through comprehensive analysis, no research results have been found
that integrate different blockchain interoperability, smart
blockchain and blockchain supervision as a whole to
guide the application of smart cities.
Overall structure of the blockchain
For the data that are generated or operated in the operation process of a smart city, because their capacity is
great, this paper proposes that the data and its corresponding blockchain (the blockchain is constructed by
the smart city perception subsystem or application subsystem) adopt the mode of data collaboration on and
off the blockchain, i.e. a structure in which the blockchain and fundamental data are stored separately, but
the correlation or link relationship between data and
the leaf nodes of the blockchain are maintained. Thus,
the data of the subsystem of the smart city may be linked
correspondingly with public blockchain, consortium
blockchain, and private blockchain respectively. Referring to the structure in Figure 2, the overall structure
of the blockchain in the smart city is shown in Figure 3.
Figure 3 is an abstract overall architecture of blockchain in the smart city. According to the differences of
the structure and functions of the database, the actual
overall architecture of blockchain is more complex
than that shown in Figure 3. Due to different business
contents, different subsystems of the smart city construct
different public blockchain, consortium blockchain, and
private blockchain. The data that are introduced from
Internet or other systems outside the smart city system
can run in the public blockchain, consortium blockchain,
and private blockchain, and are stored in the databases
(Corresponding to the shared database, authorized
access database, or private database respectively.) of
different subsystems.
It can be seen from Figure 3, that because the blockchain and its corresponding data are stored separately,
the blockchain does not change the basic relationship
as the business operation, business cooperation, and
data interaction, etc. among different subsystems of the
smart city, but only serves as the infrastructure of the
data management of the smart city. Blockchain is used
to record the production, operation and change process
of the data, so as to ensure the credibility of the smart city
data.
Cross-blockchain interoperability
The database corresponding to the consortium blockchain needs access authorization. The subsystem corresponding to the smart city and its business relationship
are complex, dynamic, and extensible, while the construction of the blockchain and its consensus authentication process will consume many resources. Therefore, in
the operation of the smart city, it is impossible to randomly construct the consortium blockchain system
according to the business requirements and business
changes. According to the business requirements, different consortium blockchains that corresponding to different subsystems can mutually record the data resources
that are authorized access, that is, mutually record can
be realized through the cross-blockchain interoperability
of the consortium blockchain. The basic principle is:
according to specific business requirements and under
the condition of authorization, the application subsystem
unconventionally accesses the authorized access database
of this application subsystem or other subsystems (application subsystem or perception subsystem), and the
related access data(hash value style) are recorded in the
consortium blockchain that corresponds to the business
requirements, and the related accessed data(hash value
style) are also recorded in the consortium blockchain
that corresponds to the accessed authorized access database (In this paper, the data are produced through the
cross-blockchain interoperability of the consortium
blockchain, and the generated data (different styles) are
recorded in different authorized access databases that
correspond to different consortium blockchains, respectively.). The mutual access of different consortium blockchains is shown as the interoperability between
consortium blockchain 2 and consortium blockchain 3
in Figure 3. The shared databases corresponding to the
BUILDING RESEARCH & INFORMATION
9
Figure 3. The overall structure of the blockchain in the smart city.
public blockchain are completely open, and the access
to the data of the shared database does not need be
authorized, so its cross-blockchain interoperability is
relatively simple. The private database corresponding
to the private blockchain is privatized, and generally
other subsystems will not access the private database
of a certain subsystem, that is, other blockchains
usually do not establish cross-blockchain interoperability with the private blockchain. It needs to be said that
clearly, the analysis of the characteristics of crossblockchain interoperability of consortium blockchain,
public blockchain, and private blockchain in here is
corresponding to the definitions of consortium blockchain, public blockchain, and private blockchain in
this paper, and its application scope is limited to this
paper. In this paper, we take the cross-blockchain interoperability of different consortium blockchains as the
research object to introduce the cross-blockchain interoperability of different blockchains. For other types of
cross-blockchain interoperability (between different
public blockchains, and between different public blockchains and consortium blockchains, etc.), its operation
principle can refer to the cross-blockchain interoperability of the consortium blockchains, which will not
be discussed in detail in this paper. The cross-blockchain interoperability process of the consortium blockchains is shown in Figure 4.
The interoperability of consortium blockchains is
dynamic and random, so, it is necessary for the regulators auditing access requirements from application subsystem I. The verification result is digitally multi-signed
by the regulators and sent to the corresponding related
business subjects, the specific implementation principle
can be seen in section ‘The supervision system for
blockchain’.
Smart blockchain
With the development of blockchain application technology, the construction and application of smart contracts in the blockchain operation systems have been
greatly developed. The representative application of
smart contracts is Ethereum blockchain, while in the
smart city application system, through the simple construction and operation of fixed smart contracts, the
blockchain cannot complete the data scheduling and
business cooperation between different subsystems of
the smart city, under the dynamic business requirement
of the smart city, the blockchain itself must own the ability of smart change, that is to say, the blockchain system
used to support business cooperation and trust guarantee
in the smart city must be smart blockchain, and the
blockchain itself has the ability of dynamic construction
for the environment, so as to ensure the effective operation of smart city businesses.
10
Y. FU AND J. ZHU
Figure 4. The cross-blockchain interoperability process of the consortium blockchain.
According to the technical characteristics, functions
and work principles of the blockchain, the wisdom of
the smart blockchain is mainly reflected in the construction of smart contracts, the selection of authentication nodes, and the storage management of data (For
the storage management of blockchain-related data,
because there are many existing research results, and
the research results have corresponding guiding significance for this paper, so, here, the issue will not be discussed further.). The smart contract of the smart
blockchain needs to be built dynamically according to
the business requirement, that is to say, the construction of the smart contract must be smart. The selection
of the authentication nodes of the smart blockchain
needs to be realized dynamically, and the selection
needs to be completed according to the business
requirement and the relationship among the corresponding business cooperation subjects.
(1) The construction of a dynamic smart contract
The idea of the dynamic smart contract is to build a
smart contract generator according to the business function of the application subsystem. The smart contract
generator dynamically generates the smart contract
according to the business started by the specific application subsystem. The regulators audit the rationality
Figure 5. The construction principle of a dynamic smart contract.
of the dynamic smart contract, and the approved smart
contract will complete the operation and management
tasks of the specific business. The auditing process of
the regulators to the dynamic smart contract can be
seen in section ‘The supervision system for blockchain’.
The construction principle of a dynamic smart contract
is shown in Figure 5.
As shown in Figure 5, the application subsystem first
judges whether the requirement is a classical business
requirement, if it is a classical business requirement,
then it calls the corresponding business collaboration
smart contract that has already been used by the system, runs the smart contract in the blockchain, and
records the data operation process and operation
results. If the requirement is a new business requirement, then the smart contract generator will produce
a new business collaboration smart contract, and the
regulators audit the rationality of the smart contract.
For the problem of a new smart contract generation,
if the adjustment number of times of its smart contract
generation parameters is less than a certain critical
value (the critical value is the maximum adjustment
number of times allowed by the smart contract generator, assumed in this paper as Q), then the smart city will
designate a management department to adjust the parameter values automatically, and if the adjustment
number of times of its smart contract generation
BUILDING RESEARCH & INFORMATION
parameters is greater than the critical value, then application subsystem I will designate a specific management
department to construct a reasonable smart contract
manually.
(2) The selection mechanism for authentication nodes
Due to the privatization and data confidentiality
requirements of the specific subsystem business in
smart cities, the operation of blockchain requires
high resource consumption. For consortium blockchains, private blockchains and some public blockchains, the authentication of blockchain data can be
realized by a small number of trusted nodes, and it
is necessary for constructing multi-authentication
centres to solve the shortage of independent authentication centre, and avoiding the problem of resource
consumption induced by complete decentralization, as
a result, multi-authentication centres are more objective for the effective operation of smart cities and consistent for the business operation requirements of
different subsystems. The selection mechanism of
authentication nodes is to solve the problem of authentication node selection when the application subsystem
faces a specific business. The selection of smart blockchain authentication nodes follows the principle of
business ownership, for the collaborative business
activities, the business subjects belonging to different
subsystems need to participate in the authentication
at the same time, if the business cooperation activities
are also relative to regulators, the regulators also need
to participate in the authentication. Due to the
businesses of different subsystems in a smart city are
complex, so the authentication subjects of different
businesses are vary, and the selection of the authentication subjects is decided by business characteristics, for
business involving multiple business departments, the
authentication subjects need to be selected from the
corresponding multiple business departments. For the
classical business activities, if there is no change in
the function and structure of different business collaboration subsystems, then the classical structure mode of
authentication nodes will be used. For new business
activities, or when the function or structure has changed in business collaboration subsystems, the authentication node composition needs to be dynamically
adjusted according to the selection mechanism of the
authentication nodes.
The supervision system for blockchain
The blockchain supervision system for the smart city is
corresponding to the business operation supervision
11
system for the smart city subsystem. The smart city
can build different blockchain supervision systems
according to different business requirements. The main
supervision contents of the blockchain supervision system of the smart city include: the supervision for the
business operation process, the authenticity traceability
of the relevant data of the business operation, the rationality verification of the smart contract, the identity verification of the authentication nodes, and the security
evaluation of the blockchain, etc. Among them, the
implementation method of business operation process
supervision is: different regulators audit the relevant
operation business in the blockchain respectively, the
approved business is digitally signed by different regulators, to form multi-signed business data, and the multisigned business data are broadcasted in the subsequent
corresponding business blockchain system, or the audit
passed signals are directly transmitted to the relevant
business subjects. In the following, from three aspects
to introduce the functions of blockchain regulators,
they are: the rationality verification of the smart contract,
the identity verification of the authentication nodes, and
the security evaluation of the blockchain.
(1) The rationality verification of the smart contract
The rationality verification of the smart contract is
usually completed by different regulatory departments,
and is completed by the nodes through algorithm analysis. The specific principle is shown in Figure 6.
(2) The identity verification of the authentication nodes
In the public blockchain system, the identity of the
authentication node is anonymous, and the mode of
the authentication node joining the public blockchain
is open. Due to the mutual independence of each subsystem business and the specialization of business
cooperation in the smart city, there are requirements to
the identities of authentication nodes of consortium
blockchain, which requires the identities of the authentication nodes need be audited before they join the consortium blockchain. For the node with reasonable identity,
the system authorizes it as an authentication node, and
for the node with unreasonable identity, the system
needs to enable the early warning mechanism, because
the node with unreasonable identity but applying for
authenticating could be a malicious node. The identity
verification process of the authentication node can
refer to the flow of Figure 6, which will not be described
in more detail here.
12
Y. FU AND J. ZHU
Figure 6. The verification principle of the rationality for the smart contract.
(3) The security evaluation of the blockchain
Because the classic blockchain has deficiencies in the
function structure and operation mode, and the mode
structure of the blockchain in different fields is variable,
so it is necessary to evaluate the blockchain security by
the regulators. Without security guarantee, the trust
guarantee function of the blockchain operation system
is also unreliable. The content of the blockchain security evaluation includes: the security evaluation for the
nodes of blockchain, the security evaluation for the
physical architecture of the blockchain, the security
evaluation for the data storage of the blockchain, and
the security evaluation for the data structure mode of
the blockchain, etc. The security evaluation of the
blockchain from the regulators and the operation of
the blockchain system are carried out separately, and
the evaluation can be realized by building a static or
dynamic evaluation system. The specific implementation of security evaluation can be carried out by referring to the relevant national or industrial standards of
the information system security risk evaluation system,
or the special evaluation system can also be developed
by the urban government departments according to
the characteristics of the smart city.
Results
Making the smart transportation subsystem as an object,
through algorithms, and from three aspects (the crossblockchain interoperability of the consortium blockchains, the construction and verification of the dynamic
smart contract, and the selection and verification of the
authentication nodes), to research the construction of
the trust system based on blockchain. For the convenience of research, using ‘st gr’ denote ‘geographic route
of smart transportation’, using ‘st sm’ denote ‘security
management of smart transportation’, using ‘st sb’
denote ‘safety database of smart transportation’, using
‘GR BC’ denote ‘blockchain for geographic route of
smart transportation’, using ‘SM BC’ denote ‘blockchain
for security management of smart transportation’, using
‘ins i’ denote ‘institution i’, using ‘ins j’ denote ‘institution j’, using ‘reg’ denote ‘regulators’. Using ‘bus req’
denote ‘business requirement’, using ‘STS’ denote
‘smart transportation system’, using ‘GIS’ denote ‘geographic information system’, using ‘SMS’ denote ‘safety
monitoring system’, using ‘WMS’ denote ‘weather monitoring system’, using ‘co sy’ denote ‘collaboration system’, using ‘sma con’ denote ‘smart contract’, using ‘gr’
denote ‘geographical route’. Using ‘au nod’ denote
‘authentication node’.
(1) Cross-blockchain interoperability for the smart
transportation subsystem
In the smart transportation subsystem, vehicles need
to travel under the guidance of geographic information
system, safety monitoring system, weather monitoring
system, and other systems, and the travel scheme can
be determined when the transportation subsystem and
different perception subsystems cooperate with each
other. However, because it is different for the influence
degree and influence mode of different perception subsystems to the decision-making of the transportation
subsystem, so usually different consortium blockchains
BUILDING RESEARCH & INFORMATION
are constructed for the interaction of transportation subsystem and different perception subsystems, and different consortium blockchains access each other
according to specific requirements.
The smart transportation geographic route blockchain and smart transportation safety blockchain are
two consortium blockchains, making the cross-blockchain interoperability between these two blockchains as
an example to research, the implementation principle
is shown in algorithm 1.
13
the travel department of the transportation subsystem,
and the geographic information management organization, etc. After the verifications are passed, the regulators sign the smart contract respectively and broadcast
it to the blockchain operation system for implementation. The implementation principle is shown in algorithm 2.
(2) The construction and verification of the dynamic
smart contract of the smart transportation
subsystem
The dynamic smart contract of the smart transportation subsystem needs to be built according to the
specific business requirements. Making the travel geographic route of the smart transportation subsystem as
an example to analyse, the route needs to be confirmed
according to the traffic conditions provided by the geographic information system. The verification basis of
the corresponding smart contract includes: whether the
smart contract has completed all the tasks of the selection for the transportation route, whether the scheme
formulation has leakage that can be improved further,
whether the route selection is objective and feasible,
etc. The smart contract that is constructed and passed
needs be audited by the regulators, the regulators are
(3) The selection and verification of the authentication
nodes for the smart transportation subsystem
Selection and verification need to combine specific
business to confirm, avoiding the excessive consumption of resources. The rule is: ensuring all business-relevant departments (assuming the amount is M)
participate in the verification, the number of total
authentication nodes aims to not exceed a limit value
(assuming the limit amount is N ), and the identities
of the authentication nodes are audited by the regulators, etc. The implementation principle is shown in
algorithm 3.
14
Y. FU AND J. ZHU
represented by algorithm 1, 2, and 3 are not isolated,
but integrated with other business activities. So, although
the fundamental principles of these algorithms are relatively simple, but the business operation processes represented by the algorithms are interactive and complex.
Because the content and process of the algorithms conform to the fundamental principles of information, technology and business processing, so this paper will not
specifically verify these three algorithms.
Discussions
Through constructing the interconnected blockchain
system for the smart city, different blockchains access
and communicate each other with protocols, constructing dynamic smart contracts for different blockchains,
and constructing the node selection mechanism in the
operation process of the blockchain, a complete data
trust guarantee system for the smart city is produced.
In the process of the smart city operation, the regulators
and the corresponding supervision mechanism provide
guarantee for the effective operation of the smart city.
Section ‘Results’ is the algorithm principle for the construction of the blockchain system of the smart transportation subsystem. The specific blockchain system needs
to be specifically designed with the development and
application level of the smart transportation subsystem
and the smart city. Under the current development
level of smart transportation subsystem, the blockchain
architecture will be relatively simple, the smart blockchain and the selection method of the consensus authentication nodes will be relatively fixed, and there will be
more artificial participation. When the development
level of the smart transportation subsystem is relatively
mature, the blockchain architecture will be more complex, almost all smart transportation businesses will be
able to operate under the guarantee of the blockchain
system, the functions of the blockchain will be divided
in detail, the interactions between different blockchains
will be frequent, the smartness of the smart blockchain
and the selection method of the consensus authentication nodes will be very high, the artificial participation
will be less, and the automation of the system operation
will be very high.
Algorithm 1, 2, and 3 provide the brief principles of
business implementation. The smart city system is a
real-time operation system. In the blockchain system
for a specific environment, the business activities
Information is an important content for the construction
of smart cities (Jiang, 2020; Wang et al., 2012), however,
in the existing research, the discussion on the trust guarantee for the information of smart cities is insufficient.
Blockchain technology can build an effective trust guarantee system for a smart city, and improve the operation
efficiency of the smart city.
The application of blockchain will have a transformative impact on urban information system architecture,
operation mode, decision-maker’s management mode
and people’s lifestyle, which is mainly embodied in the
following:
(1) The blockchain will realize the joint management
and decision-making of different business subjects
to a certain business, and the network supervision
of the regulators to the operation of the blockchain.
Blockchain will promote the high integration of the
urban network system, and the reliability and security of the business operation.
(2) Due to the application of blockchain technology,
information sharing and interaction will become
the main content of urban operation. Urban management will change from an offline mode to online
mode, and from manual participation to system
automation operation.
(3) The blockchain system will realize the automation,
openness and transparency of urban business management, and will avoid the lack of subjectivity of
traditional urban system decision makers.
(4) Due to the application of blockchain systems, the
smartness of smart city will be strengthened, the
security and reliability of network business will be
further guaranteed, people’s lives will be more
dependent on the network, and people’s lives will
become more comfortable.
For the value of blockchain to smart cities, Chen et al.
(2018) analysed the function of blockchain in promoting
the information sharing of smart cities, but the research
was only a brief analysis, and had not formed the data
BUILDING RESEARCH & INFORMATION
application mode and sharing mode based on blockchain. In this paper, according to the data sharing authority, the sharing mechanism for different types of data
in the smart city based on blockchain was proposed.
Although Wang (2018) discussed the value of the blockchain in constructing big data platform for the smart
city, the generation and operation principle of data was
not provided, making it difficult for readers to understand how the smart city operates under the blockchain
technology system. Similarly, Gong et al. (2019) proposed a framework for the blockchain applying in device
management of IoT, but because the authors had not
proposed the system architecture of the smart city
based on blockchain, the readers cannot really understand the status and operation method of the blockchain
in the smart city system, and cannot ensure the feasibility
of the application for the blockchain in the smart city.
The originality in this work is that we constructed the
architecture of the blockchain applied to the smart city
and put forward the specific implementation mode,
which was necessary for the initial stage of application
research on the blockchain in the smart city.
This research has its own limitations, which are:
(1) Lack of verification in the real environment. The
development of smart cities is not mature, and the
application research of blockchains is also in its primary stage. This paper proposes the scheme of
applying blockchains to smart cities, but it has not
formed a specific application product.
(2) Lack of analysis on blockchain construction cost. To
build a blockchain system in the smart city system,
the cost must be very high. Which institutions will
bear the construction cost and operation cost, and
the feasibility of cost investment, etc. need to be
further demonstrated.
(3) Lack of evaluation on application effect. As a new
technology system, the application of blockchain in
smart city systems needs to solve many problems
and challenges. This paper does not predict and analyse the application effect, nor does it put forward
the ideas on how to solve the difficulties to be
encountered.
Conclusions
The construction of smart cities has attracted the attention from the information developed countries all over
the world, however, the construction is still in its primary
stage. One of the key factors affecting the construction of
smart cities is that the network trust infrastructure cannot meet the needs of smart city operation. Regardless of
the application or academic aspect, the construction of
15
trust infrastructure in smart cities referred to other network systems, which also made smart cities have the
same security and trust leaks as other systems. The
blockchain can build trust infrastructure for the network
system, which has also attracted attention from academic
fields, however, the research on blockchain in smart
cities is still in the discussion and analysis stage, and
there is no framework system to guide the implementation or valuable application scheme. Based on this,
this paper proposed to apply blockchain technology to
the smart city, and as its trust infrastructure. Compared
with other similar researches at present, this paper combined the network architecture and data architecture of
the smart city, constructed the architecture system of
blockchain applying in the smart city, put forward the
specific implementation method, and designed the
models and algorithms. This paper’s research has strong
foresight and practicability, has certain guidance for the
construction of trust infrastructure and information
ecology of smart cities, and has certain reference value
for research on blockchains in other fields.
In the future research, targeted blockchain system
architecture and implementation scheme will be proposed for a specific application environment, a specific
application system will be constructed, data operation,
security and trust tests will be conducted, and the
deficiencies of the architecture system will be evaluated
and improved, so as to effectively promote the integration of blockchains and the smart city.
Acknowledgements
This work was supported by the National Social Science Fund
of China under Grant 18BTQ083.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Funding
This work was supported by the National Social Science Fund
of China [grant number 18BTQ083].
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