Efficient Transaction Processing in Byzantine Fault Tolerant Environments

The overarching goal of any state-of-the-art blockchain application [5] is ensuring the integrity of the client transactions. A blockchain in its simplest form is a linked-list, which helps to maintain a stable and reliable storage of client transactions. Blockchain has acted as a resolve to challenges in food production [7], energy trading [22], managing health care [4, 9, 16], and insurance fraud prevention [14]. The key reasons behind widespread interest in blockchain systems are their fundamental characteristics: transparency, integrity and decentralization. A blockchain supports transparency and decentralization, by employing the core database principle of replication. Each blockchain is maintained by several replicas. These replicas need to reach an agreement on the order of client transactions, which is resolved by employing a consensus protocol. Thus, at the core of any blockchain system is its underlying consensus protocol. Intial blockchain applications, such as Bitcoin [20] and Ethereum [25] encourage a permissionless setting through the use the Proof-of-Work [10, 15] (PoW) protocol to attain consensus. PoW requires each replica to spend its resources in finding a solution for some hard cryptographic puzzle, which acts as a proof that the replica has generated the next block. Hence all the replias reach a consensus when at least one replica transmits its proof to the majority of replicas. However, PoW protocol can lead to the case where multiple replicas can claim to have generated the proof, which could create a fork in the blockchain. ∗https://gupta-suyash.github.io/ †https://jhellings.nl/ ‡http://thamir.qadah.com/ §https://sajjadrahnama.com/ ¶https://msadoghi.github.io/