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Generalized Proof-of-Activity (PoA) With a Forking Free Hybrid Consensus

Bitcoin and the blockchain technology in general have attracted considerable attention during the past few years. One of the blockchain main innovations is proof-of-work (PoW) which is relatively inefficient and promotes centralization of computational power; this leads to deviation from the main goal of cryptocurrencies; decentralization. Proof-of-stake (PoS) was later proposed to substitute for PoW. Nevertheless, both of PoW and PoS possess various innate merits and demerits, similarly to proof-of-activity, which was proposed by Sigmetrics in 2014 and offers a combination of both mechanisms. Furthermore, the hybrid consensus was recently proposed to boost efficiency via dynamic maintenance of a rotating committee. However, the hybrid consensus is associated with issues related to selfish mining and fairness of the process of election of committee members.

A recently published paper proposed a new variant of PoW which was utilized by its creators to build a forking free hybrid consensus, that can mitigate issues associated with the conventional hybrid consensus protocol. The authors of the paper also combined their novel forking free hybrid consensus scheme with PoS aiming at generalizing PoA. Apart from the previously described PoA protocols, the proposed PoA maximizes efficiency and offers a more resilient combination of PoW and PoS, yielding a more efficient and applicable consensus protocol.

An Overview of the forking free hybrid consensus scheme:

The proposed generalized PoW is based on a forking free hybrid consensus in order to provide an innovative way of freeing the hybrid consensus protocol of forking and combine the hybrid consensus protocol with a voting-based incentivizing negotiation system to provide rewards for honesty. The proposed forking free hybrid consensus protocol is characterized by the following:

Forking free PoW:

The design of the new PoW protocol eliminates forking. Accordingly, selfish mining will be prevented and the system’s overall security can be maximized. Moreover, wasting of enormous amounts of resources, via following the blockchain “wrong” branches, can be prevented.

Precise evaluation of processing power:

Generalized PoW is characterized by minimal evaluation of the processing power of the committee’s participants. Throughout their paper, the inventors of the new scheme proved that generalized PoW exhibits minimal variations in the process of evaluation of the PoW capability of the committee’s participants.

Incentives for honesty:

Throughout their work, the inventors of the scheme provided a voting-liked incentive negotiation protocol which provides rewards for honest committee members. Whenever members of the committee behave dishonestly, they will lose block rewards and transaction fees.

PoA is improved to render it more efficiently applicable. To achieve this, generalized PoA is proposed, which is a generalized construction form of PoA leveraged via the novel forking free hybrid consensus. Oppositely to the original PoA scheme, the proposed generalized PoA offers the following advantages:

Forking free PoA with efficiency:

In the original framework of PoA, forking is still essential to deal with possible ambiguity occurring during the process of mining of blocks. Considering the proposed generalized PoA, instead of utilizing Nakamoto’s chain as the basic protocol, dynamic maintenance of a committee is achieved via means of a generalized PoW forking free protocol in order to confirm transactions via a PBFT network, aiming at achieving the “forking free” characteristic along with maximum efficiency.

Flexible and formalizable combination of both PoW and PoS:

Oppositely to the original design of PoW, the newly proposed generalized PoA relies on generalized PoW, which gives users of the protocol the chance to flexibly select how to achieve an efficient combination of PoW and PoS. Additionally, the new generalized PoW is extremely easy to be analyzed in a formal manner. The paper also delves into “concave” combination choices.

Advantages of Generalized PoW:

The following represent the advantages of the generalized PoW protocol:

1- Elimination of forking. Forking leads to wastage of an enormous amount of processing power of miners who follow the “wrong” branches of the blockchain.

2- Friendliness to network delays. Generalized PoW is found to be more friendly to nodes that face network delays. The authors of the paper proved this in a separate appendix in the published paper.

3- Fair evaluation of processing power. Using formal comparisons, the authors of the paper showed that generalized PoW provides satisfactory levels of accuracy along the process of processing power evaluation in comparison with the conventional construction.

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