Beating the Fault-Tolerance Bound and Security Loopholes for Byzantine Agreement with a Quantum Solution
Chen-Xun Weng,
Rui-Qi Gao,
Yu Bao,
Bing-Hong Li,
Wen-Bo Liu,
Yuan-Mei Xie,
Yu-Shuo Lu,
Hua-Lei Yin,
Zeng-Bing Chen
Affiliations
Chen-Xun Weng
National Laboratory of Solid State Microstructures and School of Physics, Collaborative Innovation Center of Advanced Microstructures,
Nanjing University, Nanjing 210093, China.
Rui-Qi Gao
National Laboratory of Solid State Microstructures and School of Physics, Collaborative Innovation Center of Advanced Microstructures,
Nanjing University, Nanjing 210093, China.
Yu Bao
National Laboratory of Solid State Microstructures and School of Physics, Collaborative Innovation Center of Advanced Microstructures,
Nanjing University, Nanjing 210093, China.
Bing-Hong Li
National Laboratory of Solid State Microstructures and School of Physics, Collaborative Innovation Center of Advanced Microstructures,
Nanjing University, Nanjing 210093, China.
Wen-Bo Liu
National Laboratory of Solid State Microstructures and School of Physics, Collaborative Innovation Center of Advanced Microstructures,
Nanjing University, Nanjing 210093, China.
Yuan-Mei Xie
National Laboratory of Solid State Microstructures and School of Physics, Collaborative Innovation Center of Advanced Microstructures,
Nanjing University, Nanjing 210093, China.
Yu-Shuo Lu
National Laboratory of Solid State Microstructures and School of Physics, Collaborative Innovation Center of Advanced Microstructures,
Nanjing University, Nanjing 210093, China.
Hua-Lei Yin
National Laboratory of Solid State Microstructures and School of Physics, Collaborative Innovation Center of Advanced Microstructures,
Nanjing University, Nanjing 210093, China.
Zeng-Bing Chen
National Laboratory of Solid State Microstructures and School of Physics, Collaborative Innovation Center of Advanced Microstructures,
Nanjing University, Nanjing 210093, China.
Byzantine agreement, the underlying core of blockchain, aims to make every node in a decentralized network reach consensus. Classical Byzantine agreements unavoidably face two major problems. One is 1/3 fault-tolerance bound, which means that the system to tolerate f malicious players requires at least 3f + 1 players. The other is the security loopholes from its classical cryptography methods. Here, we propose a Byzantine agreement framework with unconditional security to break this bound with nearly 1/2 fault tolerance due to multiparty correlation provided by quantum digital signatures. It is intriguing that quantum entanglement is not necessary to break the 1/3 fault-tolerance bound, and we show that weaker correlation, such as asymmetric relationship of quantum digital signature, can also work. Our work strictly obeys two Byzantine conditions and can be extended to any number of players without requirements for multiparticle entanglement. We experimentally demonstrate three-party and five-party consensus for a digital ledger. Our work indicates the quantum advantage in terms of consensus problems and suggests an important avenue for quantum blockchain and quantum consensus networks.
