Proof of Activity: Extending Bitcoin's Proof of Work via Proof of Stake

Abstract

We propose a new protocol for a cryptocurrency, that builds upon the Bitcoin protocol by combining its Proof of Work component with a Proof of Stake type of system. Our Proof of Activity (PoA) protocol offers good security against possibly practical future attacks on Bitcoin, and has a relatively low penalty in terms of network communication and storage space. We explore various attack scenarios and suggest remedies to potential vulnerabilities of the PoA protocol, as well as evaluate the performance of its core subroutine. 1