Review on Consensus Protocols for Blockchain

Blockchain has been an important keyword in many real-time applications such as sharing a secure medical data, online payment, supply chain, identification mechanisms etc. Different types like Permission less and Permissioned blockchain serve as their requirements on various applications such as Permissioned blockchain is beneficial for resource constraint devices in terms of storage, energy, resources, and efficiency. Permission-less blockchainis efficient for those devices that have a lot of resources and energy. The consensus is a term used in all types of blockchain, which place themselves in the important place of bringing all institutions together in one agreement. The consensus protocol plays an important role in preventing attacks and also keeping the stability of nodes in blockchain systems alive. In blockchain systems, consensus protocols are an important contribution to maintaining security and scalability. They maintain the order of fixed nodes and also activate nodes for correct information. In this paper, the blockchain consensus protocols based on different types of blockchains are analyzed. Finally, we will evaluate the protocols through comparison tables and some factors such as persistence, robustness, efficiency, rigidity, stability, and optimality, etc., known as PREStO.