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                              Qian ZHANG earth01 (3K)
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Tencent Professor of Engineering,

Chair Professor of

Department of CSE,

HKUST

FIEEE,

Changjiang Chair Professor, Huazhong University of Science and Technology (2012-2015)

 

Co-Director and founder, Huawei-HKUST Innovation Lab

Director, Digital Life Research Center, HKUST

 

HKUST IAS Senior Fellow

 

My Citations (Google Scholar click here)

 

Department of Computer Science and Engineering

Hong Kong University of Science and Technology

Clear Water Bay, Kowloon

Hong Kong

 

Email: qianzh@cse.ust.hk

URL: http://www.cs.ust.hk/~qianzh

Office: Room 3533 (via Lift 25-26), Academic Building

Tel: 852-23588766

Fax: 852-23581477










An efficient blockchain infrastructure construction

Today’s global financial system is inefficient and vulnerable to failures and attacks due to its centralization and antiquation. Thus, blockchain, a decentralized, distributed and public digital ledger shows great potential to enhance or even revolutionize the financial ecosystem. Unfortunately, scalability is a huge problem which causes its low efficiency. As a result, current blockchain system can be hardly used under the scenario of IoT. Sharding is one of the most worth expecting technologies to improve the system's throughput by processing transactions in parallel. However, the state-of-the-art sharding based system has two main disadvantages lead to the inefficiency: (1) Their systems are lack of the proper incentive mechanism. (2) Their systems require a larger shard size to increase the low-security level baseline.

Prof. Zhang's group introduced reputation scheme to build up a high-efficiency blockchain system. Reputation scores of all the validators are measured based on their behaviors. A reputation based sharding and leader selection scheme maintains a balanced sharding to enhance the security and incent the validators. However, there remains a significant challenge to achieve a secure, high incentive and fast blockchain system: how to design an efficient consensus under such assumptions.

Prof. Zhang's group have proposed a reputation based blockchain system to overcome the above two challenges. The key idea is the double-chain architecture that leverages a reputation chain with moderate generation speed to support the high throughput transaction chain. The reputation chain records the validators’ reputation based on their behaviors. Also, a reputation based sharding and leader selection scheme maintains a balanced sharding to enhance the security and incent the validators. The transaction chain is generated via a Raft-based synchronous consensus which achieves high throughput and high resiliency by effectively utilizing the capability of competent shard leaders. All these designs combining together realize a secure, high incentive and fast blockchain system.

In the future, Prof. Qian’s team will continue on the research of blockchain in different directions. The first direction is the incentive mechanism. The reputation scheme mentioned above is a prototype which has a great room for improvement. They will try to design a novel reputation scheme that can unleash the power of reputation by game theory and other models. Besides, they will also study on the incentive model in blockchain token generation which is an important problem among all blockchain systems. Consensus design is another direction. The above proposed scheme utilizes a Raft-based protocol for transaction chain to guarantee the efficiency which still faces challenges in other aspects. How to design a consensus that can reach the best trade-off among all the sides, including efficiency, decentralization, and security, is challenging. PBFT, hierarchy, and off-chain are all possible approaches. With the assist of reputation scheme, it would be promising to design a better solution comparing with current consensuses. The last but not the least, how to implement blockchain for the Internet of Things is a crucial direction. It needs the additional design to deal with the low performance and low capability of IoT devices. Also, how to enable smart contract and other practical elements should be studied. As a whole, these research directions will try to utilize the reputation to design a blockchain system that can be really deployed in our future life.