Abstract:
Blockchain has caught the attention of both researchers and industrialists because of its widespread growth in the last 10 years. What was started with decentralized immutable ledger has now paved its way to decentralized, open access and self-organizing networks and journey has just begun. These characteristics like decentralization, immutability, open access, liveliness and trust are achieved through consensus protocol employed by specific Blockchain. A consensus protocol allows a group of separate nodes to distribute the right to update the system according to specific rules, amongst a set of participants, and in a secure way. A plethora of such consensus protocols have been proposed since last few years. HO\vever, not all those protocols are as robust as others and existing systems in the same domains. few offer higher security guarantees than others and have their unique performance characteristics. One mechanism will not fit every envisaged application and use case of block chain. This mandates that such protocols be compared for their security and performance parameters to gain a comprehensive overview of their strengths and weaknesses. This research covers a comparison of nine consensus protocols designed to operate in private, consortium and public blockchain settings belonging to different eras of protocols design and enhancements. Current research provides an overview of generic functioning of blockchain and a summary and guideline for application developers to choose a consensus protocol for their applications that best match their requirements and quick reference for those protocols for the academia - doing so it also provides recent directions in consensus designing landscape. Keywords Blockchain Consensus, Distributed System Consensus, Blockchain System. Blockchain Design, Asymmetric Cryptography, Hashing. Bitcoin, Nakamoto Consensus, Bitcoin-NG, Proof of stake, Ouroboros, Preas, PBF.
