Why QLC Chain utilises the dual-consensus protocols of DPoS and PoW

QLC Team
QLC Team
Dec 19, 2019 · 5 min read

The past 11 years have seen the development path of consensus protocols adopted by blockchains, among which PoW and PoS are the proven viable ones. The improvement of these two consensuses has never stopped and there are various blockchain projects continuously contributing to their evolution. QLC Chain is one of them.

The PoW and PoS consensus protocols are known for the following issues when being adopted in practice:

  1. Scalability is one of the most critical issues of consensus protocols, as well as the measurement of a blockchain’s performance.
  2. The issue of centralization is a concern with both PoW and PoS.
  3. PoS is the first consensus that combines token staking with PoW for security and decentralization, however this approach has caused new problems such as long range attack, and higher level centralization

To resolve the existing puzzles, QLC Chain utilises the dual consensus protocols of DPoS and PoW which unify the computational power jointly contributed by mining and voting nodes, thus providing a higher level of security, efficiency and scalability.

  1. On-chain transaction validation process through voting by stake and PoW

Firstly, each transaction is initially confirmed via the DPoS consensus.

Secondly, after the transaction validation by voting nodes, the transaction enters the unpacked PoW pool.

Thirdly, the transactions in the unpacked PoW pool are then mined into PoW blocks that form the PoW Chain.

The voting nodes and the PoW mining nodes are independent as shown in the following demonstration:

2. QLC Chain consensus protocol combining the advantages of Staking and PoW

Compared to PoS, QLC Chain dual consensus offers the following improvements:

2.1 Balanced efficiency and decentralization

By adopting the dual-consensus protocol, a transaction is validated through the two separate steps and guarantees trustworthiness, so the PoW Chain blocks only need to store the data of the transaction hash rather than the raw data. This way, the transaction processing performance of PoW is largely improved which results in greater efficiency and scalability of the QLC Chain.

PoW as the second layer requires the work of the mining nodes with greater computing capabilities to solve problems and generate new blocks, so that the staking holders possessing a large proportion of assets can not solely make decisions for the entire network.

2.2 Providing the possibility of ledger pruning based on the two-layer structure

QLC Chain structure provides the infrastructure base on which the ledger can be pruned with the data size of the transactions stored on-chain shrinked. The working theory behind is that the transactions that have already been validated by the PoW mining nodes and packed into the PoW Chain blocks, can be removed from the account chain.

On the premises that the validity of new transactions won’t be affected, the historical transactions can be pruned off to downsize the storage taken up by the ledger.

Considering a second layer of PoW validation that the transaction has undergone and the transaction hash being written into the PoW Chain blocks, the transaction raw data can be pruned off from the accounts, thus allowing for a much smaller database size, lower disk usage, reduced processing time and faster setup of nodes.

2.3 Enhanced ledger security combining voting and mining

Each transaction will be subject to a dual consensus — DPoS and PoW. During the process of block generation on the QLC Chain, the two steps of transaction verification are separated by going through voting nodes validating and PoW mining in chronological order, with the voting and mining nodes involved working separately and independently.

If someone wants to commit a ’51 percent attack’ by rolling back a transaction, they have to undergo the validating process in reverse, firstly PoW and then voting nodes, which is extremely difficult, because a malicious node would have to possess over 51% of the PoW computational power and 51% of the voting weight out of the total circulation supply.

QLC Chain’s security level is extremely high, which prevents ledger tampering.

2.4 More democratic and inclusive on-chain governance

The list of voting nodes is dynamic, a stakeholder account is allowed to change the delegate node of its voting power at any time. Whenever a voting node is found to act malicious or missing on validating transactions, it can be voted out and deprived of the right of receiving QGas incentives from mining. In comparison with PoS, DPoS offers more governance power to the stakeholders with small stakes and efficiently incentivizes the voting nodes to execute duties.

In the case of Go-QLC Version 1.5.0 — QLC Chain, the three roles of stakeholder account, voting node and mining node also work together as a community who reserve their rights of proposing, voting on the proposed changes and resolving any issues. This way, the accounts and nodes within the QLC network are incorporated into the decision-making process. This part will be elaborated in further detail after mainnet launches.

About QLC Chain

QLC Chain is to resolve the data trust and security problem in the communication industry, and aim to build a public chain for Network-as-a-Service (NaaS) platform.

From ledger structure perspective: QLC Chain supports each account to have its own chain of ledger integrated with telecom service capabilities, named the multi-dimensional block-lattice structured ledger.

From an adoption scenario perspective: QLC Chain’s mission is to create a secure and trusted environment for communication services and to narrow down the digital divide by leveraging Distributed Ledger Technology, enabling everyone to operate and benefit from network services.

Learn more about QLC Chain https://qlcchain.org/

QLC Chain

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