First | Ant Blockchain Engineer Readme: Using Blockchain to Realize Cross-City Metro Subway Codes

Source: Ant Financial

On the first day of the Spring Festival 2020, as of that day, the number of people traveling in different places in the “Yangtze River Delta ’s major cities’ code-scanning and interoperability ”project facilitated by ant ’s blockchain increased nearly 15 times compared to last year ’s Spring Festival, and the number of access cities expanded to 11. Covering a journey of 1,842 kilometers, the cumulative savings in queuing time can fly more than 10,000 times around the earth.

Thinking back to a year ago, the first project meeting of Interconnect was held in Z Space, Xixi Road, Hangzhou, where Alipay is located. At 10 o'clock that morning, business and technical staff from metro companies in Shanghai, Hangzhou, Ningbo and other cities did not have time to check in to the hotel and dragged their suitcases to the conference room. Discuss the plan in the morning and start the development in the afternoon. After more than a month of retreat, the blockchain-based subway interconnection is finally completed. At that time, everyone was a bit exhausted. A project team member was so busy that he forgot to almost pay the mortgage. But one year later, everyone was glad that they could be part of the project. Ant blockchain engineer analyzes the application of blockchain technology behind subway interconnection.

The difficulty of travelling in different places is the real-time ticket settlement

During the Spring Festival, a white-collar worker from Shanghai returned to his hometown of Ningbo. He opened the Shanghai Metro app and said, “Beep, scan the code successfully, open the gate, and take a bus. Then, make a beep, leave the station, and take a subway trip to another place. For the individual user, he can perceive that it is a smooth code-scanning ride, but behind the sound of "嘀", there are many technical breakthroughs such as blockchain.

A major difficulty in cross-city travel is the settlement of off-site tickets, while the difficulty of off-site ticket settlement is the incompatibility of data between regions. Due to objective factors such as laws, regulations, and operating models, each city's rail transit uses independent user and data systems. The traditional data sharing model is a centralized service that matches various data providers. However, as the number of participants increases, the continued use of traditional systems will lead to three problems: the complexity of systems and engineering will increase exponentially, and the security of data will increase. Facing severe challenges, there is a lack of a mutual trust mechanism between the various parties.

Although the demand for passenger “passes” for cross-city rail transit is increasing day by day, all parties are at a loss and cannot be promoted. Behind the subway interconnectivity, a new technology product is needed to interconnect the various information islands to achieve efficient, safe and reliable sharing and collaboration of cross-city rail transit data.

Based on the Ant Blockchain Baas platform, passenger ride information for all city subways is placed on an open, unified, and secure chain, and major cities can intuitively obtain ride data from above to complete ticket settlement, which undoubtedly defeated the traditional off-site Barriers in the ticketing stage make intercity travel more convenient and efficient. With the completion of scanning by the user, the blockchain automatically realized second-level settlement.


It is worth noting that the ant blockchain uses the networking mode of the alliance chain. Ant Blockchain adopts independently developed and optimized Byzantine Fault Tolerance (PBFT) consensus mechanism, which can make the consensus speed less than 1 second, which is the powerful technical weapon behind the interconnected second-level settlement.

Interconnect with minimal cost

At the beginning of the project, everyone reached a consensus: the threshold for access to more cities was minimized.

The traditional point-to-point mesh interworking mode has the advantage of rapid interworking in a small area, but when facing more urban access, there are problems such as lack of interworking data and insufficient openness, which is not conducive to large-scale promotion. In order to achieve more efficient access to the urban rail ticketing systems in various cities, the interconnection and interconnection project introduces a blockchain service platform. Since metro apps in various cities read and write data to the blockchain, there is no need for a centralized system to ensure strong data consistency. When new participants join, they only need to dock. Blockchain will not affect existing systems.

The blockchain interworking solution has the following advantages:

First of all, the interworking QR code ride solution does not need to modify ticketing equipment, so that each connected city has full autonomy over its own AFC system, Internet ticketing system (QR code), and corresponding systems. All core The business is controlled and managed independently by the landing city, which has greater controllability and integrity.

Secondly, cities communicate with each other through SDK interoperability, unified interface specifications, and business process coupling. Each city only needs to connect to one SDK to achieve interconnection with other cities, which greatly reduces access costs and subsequent maintenance. cost.

Finally, the introduction of blockchain technology, sharing user information, travel information, and settlement information between interconnected cities through the blockchain application platform, improving the fairness and reliability of interconnected business, and at the same time carrying out information on untrustworthy users such as abnormal charge Share and promote the credit system of joint risk control.

2 Interoperability Blockchain Service Platform Solution Architecture

More secure hardware-level security protection

As an Internet application system, the entire system needs to achieve unified data security and implement data encryption methods with different keys in different cities to ensure the security of system data in each city.

Perceptually, people usually think that symmetrical things are more aesthetically pleasing, and asymmetry is imperfect. But in the field of information security, asymmetry has its own beauty. In terms of data security, Interconnection uses asymmetric keys to encrypt the data on the chain.

The core data uses an asymmetric encryption algorithm to ensure that the security of each city is independent. Blockchain data can only be accessed by interconnected members: interconnected members need to use a blockchain authentication certificate to access the blockchain, and clients access the blockchain using TLS two-way authentication to ensure the security of the data transmission process.


By using the feature that the encryption and decryption keys are not the same, but one-to-one correspondence, you can safely distribute the public key used for encryption to the data provider; at the same time, you do not need to obtain information and can verify the legality of the information. Ant Blockchain BaaS not only provides participants with more secure hardware-level key generation tools, but also makes the management of data permissions easier and more reliable in product use. Strictly proven mathematical theorems and BaaS's extensive efforts for data security work together to ensure that different types of data are efficiently transferred between the business systems of metros in the city without being acquired by any unrelated parties.

More and more urban rail transits have been connected to provide more efficient travel services for passengers.The Ant blockchain has demonstrated its ability to support data sharing and collaboration in a multi-participant scenario. The Ant Blockchain BaaS platform reduces the barriers to the use of blockchain for developers of business systems: not only can the alliance sponsors create the alliance chain in one minute, the individual participants of the alliance also need only a few simple steps to configure , You can join the alliance chain to achieve data interaction. In addition, BaaS also provides a series of value-added services (BaaS Plus) for verifying the identity and qualifications of participants, as well as privacy encryption calculation based on TEE hardware, and high-performance cross-chain capabilities between alliance chains. This is a larger-scale subway The formation of the Interconnect Alliance provides a solid technical foundation.

There are still many scenarios in business and life: capital flow between suppliers at all levels in the supply chain, core enterprises and banks; logistics and capital flow information is shared by all parties, including regulatory agencies … with the blockchain The development of technology, these pain points that were inexhaustible yesterday, have become an inspiring opportunity today. An era of industrial Internet based on blockchain is accelerating towards us.