Security and Privacy of Blockchain and Quantum Computation

Security and privacy are vital to the modern blockchain technology since it can exist without an authorized third party, which means that there may not be a trusted responsible person or organization in charge of systems. In this chapter we make a survey on this issue about blockchain systems. Security of the current systems is based on the computational hardness assumptions and many of the standard cryptography systems are known to be vulnerable against the advent of full-fledged quantum computers. On the other hand, it is possible to make a blockchain more secure by virtue of quantum information technology. In this chapter we give a pedagogical introduction to quantum information theory and quantum computation so that readers can follow advanced researches on application of quantum technology to the blockchain industry. We also explain a novel information system which accommodates quantum states in a peer-to-peer way. It would improve the level of privacy and security by the laws of physics, which is never achievable from nonquantum information theoretic viewpoints.