This survey paper is the basis for our research on Nimiq 2.0.
The area of distributed ledgers is a vast and quickly developing landscape of consensus protocols. This makes it considerably hard to gain a comprehensive overview of the current state of protocols. Many of those trade one property for another and there does not seem to be a widely accepted and clear winner in the race for the best protocol.
This paper aims at providing an overview of most of the recent directions in this landscape, not claiming completeness. Instead of completeness, it targets to deliver a solid basis for discussions about current and future developments in the field of distributed ledgers, emphasising scalability. Besides purely consensus-based scalability and sharding, we also explore off- chain scalability solutions and recent advances and implications in privacy-preserving protocols.
You can find the current draft here: