The Future of Cryptocurrency Blockchains in the Quantum Era

Cryptocurrency are decentralized digital money systems built on blockchain technology. The transactions are secured in these system using digital signatures based on public-key cryptography. Public-key cryptographic algorithms used for digital signatures, such as ECDSA, are vulnerable to quantum attacks. With over 2 trillion dollars market capitalization, the cryptocurrency industry will be at high risk in the Quantum Era. This paper evaluates the security of today's cryptocurrency blockchains under quantum attacks. It also reviews some of the proposed solutions to protect blockchains in the Quantum Era. Moreover, it presents a number of post-quantum digital signature schemes used to build quantum-safe blockchains. The result of this study shows that only a small portion of cryptocurrency can resist quantum attacks, while most of the cryptocurrencies used today are vulnerable to quantum attacks, with more than 99.8% of the total cryptocurrency market cap remains at risk. Useful recommendations are provided as a result of this study.