Cryptocurrencies without need for consensus

Cryptocurrencies like Bitcoin have revolutionized the way we think about money and transactions, mainly because of their several beautiful properties such as the lack of a single point of failure, the distributed way of generating new coins, etc. However, they come with several disadvantages that currently make them difficult to scale. Some of them are the need to maintain consensus on the whole list of transactions that can reach several gigabytes and the high communication complexity in order to reach consensus.

In this talk, we will use the power of quantum computers to propose a construction that overcomes all the above obstacles while maintaining the good properties. In particular, we will propose a scheme that does not require consensus over an evergrowing blockchain and does not assume an honest majority of the players. In the construction, we will make use of a stronger form of what we call non-collapsing collision-resistant hash-functions; i.e., collision-resistant hash-functions where it is easy to tell whether we are given a quantum superposition of several preimages of a known y, or just a single preimage.

Joint work with Aggelos Kiayias and Mark Zhandry.