A smart city will use millions to billions of teraBytes of data. There will be information and communication technology to enhance the quality of life of its citizens and improve the efficiency of urban services such as utilities, energy, and transportation. Intelligent Transportation Systems (ITS) are an integral part of smart cities. ITS use sensing, communication, analytics, and control to improve the safety and efficiency of city-wide transportation systems. Future connected vehicles interacting will be equipped with a substantial number of sensors (such as Global Positioning System (GPS), dashboard cameras, Light Detection and Ranging (LIDAR), etc.) that will produce large volumes of data. Research conducted by Intel predicts that future vehicles will produce 4,000 GB of data every day.
Existing methods to achieve data integrity and veracity suffer from the following issues:
• Centralization: most of the existing methods rely on centralized brokers, such as the vehicle manufacturer, and are unlikely to scale and accommodate millions of connected vehicles, each of which generating a large amount of sensing data.
• Lack of Privacy: the existing data exchange platforms require a vehicle to authenticate itself to ensure trust. This compromises the vehicle owner privacy as the exchanged data is now connected to their identity.
• Data Vulnerability: data collected by connected vehicles is typically stored in traditional data stores (e.g., centralized Database Management Systems), which have been shown to be vulnerable to breaches. Tampering with these data could lead to serious harm, e.g, causing accidents if the falsified data are used to control traffic lights.
Blockchain has the potential to address the data problems. It supports decentralization, security, and privacy and is being widely used in diverse disciplines including finance, law, Internet of Things (IoT) and energy.
SpeedyChain is a blockchain-based data exchange framework for smart cities. It includes smart city infrastructure (e.g., traffic lights), smart vehicles, RSIs (roadside infrastructure units), and SPs (Service Providers). The blockchain management, i.e., verification of transactions and blocks, and mining new blocks, are performed by participants that have both more available resources and a closer commitment to the smart city.
By using SpeedyChain, the participants in the blockchain can establish communication with non-repudiation, data integrity and resilience, which not only allows a vehicle to be authenticated by RSIs but also allows RSIs to be trusted by vehicles. Once the trust is established, the vehicle will have a block created on the blockchain and is allowed to append transactions to his block. To ensure user privacy, the framework proposal relies on the anonymity principle that is used in Bitcoin, thus vehicles must change their keys in defined time intervals known as key update interval (KUI). Within a KUI, vehicles must replace their current key pair by a new one and update the blockchain accordingly.
SpeedyChain is a permissioned blockchain-based framework for ensuring resilient, decentralized and immutable management of smart city data. SpeedyChain also ensures reliable Vehicle-to-Infrastructure communication and maintains vehicle privacy by employing periodically changeable keys.
In tests, they varied the number of created transactions between 10 and 1,000 and measured the time required to validate and append a new transaction in the blockchain. In our experimental results, they observed a linear growth in time and were able to show the low latency introduced by their framework (i.e., under 2 milliseconds). Consequently, the results demonstrate that through SpeedyChain usage, it is possible to exchange information in smart cities ensuring resilience, data integrity and tamper-resistance.
They provided qualitative analysis on security and privacy of their approach. Simulation results using the CORE simulator demonstrate that the proposed method is capable of maintaining the blockchain on the RSI and the latency to create blocks and transactions, as well notify the RSIs about the change, is low. We also identified that as the number of transactions generated or blocks created in the blockchain increases, the time for performing these operations increases too, however, a further research will be conducted in order to evaluate the SpeedyChain scalability in a larger scenario.
An interesting direction for future work is to define different levels of access control for the data that are produced by a smart vehicle, allowing it to define the access level. Similarly, future work should evaluate a mechanism to allow the transactions to be stored externally to the blockchain while maintaining its data sequence, integrity and non-repudiation attributes.
There is increased interest in smart vehicles acting as both data consumers and producers in smart cities. Vehicles can use smart city data for decision-making, such as dynamic routing based on traffic conditions. Moreover, the multitude of embedded sensors in vehicles can collectively produce a rich data set of the urban landscape that can be used to provide a range of services. Key to the success of this vision is a scalable and private architecture for trusted data sharing. This paper proposes a framework called SpeedyChain, that leverages blockchain technology to allow smart vehicles to share their data while maintaining privacy, integrity, resilience and non-repudiation in a decentralized, and tamper-resistant manner. Differently from traditional blockchain usage (e.g., Bitcoin and Ethereum), the proposed framework uses a blockchain design that decouples the data stored in the transactions from the block header, thus allowing for fast addition of data to the blocks. Furthermore, an expiration time for each block to avoid large sized blocks is proposed. This paper also presents an evaluation of the proposed framework in a network emulator to demonstrate its benefits.