Elastos employs a hybrid consensus mechanism of AuxPoW+DPoS for its main blockchain where each block is packaged by miners and then signed by DPoS supernodes, thereby creating a finality to blocks which prevents the blockchain from forking. Beneath the simplicity of Elastos’ hybrid consensus mechanism lies a highly sophisticated multi-stakeholder solution which provides maximum security and optimal network decentralization.
The miners who package blocks are actually bitcoin miners who merge-mine both BTC and ELA simultaneously. This means that Elastos is able to borrow massive hashpower from the Bitcoin network to secure its own. It is also noteworthy that the supernodes on Elastos are not like supernodes from other blockchain projects. On most blockchain platforms that employ DPoS consensus, the supernodes both package blocks and sign them. On Elastos however, the job of a supernode is to sign and verify the blocks. Consequently, DPoS supernodes can collectively choose to reject malicious blocks packaged by merged-miners and also provide the final stamp of validation for solved blocks – called “finality.”
The main issue with PoW consensus – apart from being computationally intensive – is that there is a high probability of a fork when the miner community is divided. For example, Bitcoin forked into Bitcoin and Bitcoin Cash. More recently, Bitcoin Cash forked further into Bitcoin ABC and Bitcoin SV. This happens whenever the community is divided and cannot reach a consensus on what features and upgrades to implement or eliminate on the blockchain. When there is enough support on both sides, the miners split up, causing the blockchain to split into multiple blockchains. In order to prevent such a catastrophic event, Elastos employs a hybrid consensus mechanism where the miner community must always follow the voice of the majority of the community members, as decided by democratic vote. The miners who do not follow these rules are deemed invalid, in which case the DPoS supernodes will not sign these particular blocks. By splitting up the power of packaging blocks and signing blocks into two different processes, Elastos creates an ingenious method to ensure finality in each block. In doing so, Elastos prevents any sort of fork occuring in its blockchain. Of course, no consensus mechanism is perfectly secure, but the hybrid consensus mechanism employed by Elastos certainly adds an additional layer of security, further strengthening the network.
In addition, there are 12 CRC (Cyber Republic Consensus) supernodes that are active at all times and are always included in the 36 active supernodes that take part in the consensus mechanism. Thus, only 24 of the 36 active supernodes are elected by the community at any one time. Because the DPoS consensus for the Elastos blockchain requires ⅔ of the active nodes’ signatures, a block must be signed by at least 25 supernodes. This creates yet another layer of security for the hybrid consensus that Elastos employs. Not only do the PoW nodes have to be compromised, but the DPoS supernodes as well. As it is already astronomically costly and difficult to amass over 50% of the Bitcoin hashpower, it will be just as hard to amass over 50% of the Elastos hashpower. Furthermore, adding the DPoS layer to the mix means that even if the PoW nodes are somehow compromised, it will be the DPoS supernodes who have the final say in which blocks to sign and which to ignore. Thus, the DPoS supernodes can collectively ignore the malicious blocks that were sent to the blockchain P2P network. Also, if we hypothetically assume the worst – that all merged-miners and all of the 24 supernodes are compromised – the best a malicious actor can do is halt the production and signage of blocks. In this circumstance, the malicious entity will be limited because it will not be able to acquire the necessary 25 signatures to validate faulty blocks. The 12 CRC supernodes, which are controlled by private keys held by the 12 Cyber Republic council members, will always act honestly and will never accept any malicious blocks, as it is in their best interest to do so. After all, each council member must deposit 5,000 ELA to be considered for the Cyber Republic election and each can be voted out by the community at any time if he or she does not act in the best interest of the collective community voice.
The DPoS consensus for the Elastos blockchain works differently than a typical DPoS consensus mechanism, with the community playing a major role in the consensus process. The PoW mining is conducted via merged-mining, a process which utilizes Bitcoin mining machines to package transactions into a block. Then, the supernodes take action by signing each block. The community can submit different proposals to Cyber Republic and may include changes to the present consensus mechanism for new sidechains or propose the creation of a new sidechain dedicated to a specific application. The proposal may also include an architectural change to be implemented on the main chain code. Should the proposal be accepted by the Cyber Republic Council, the supernodes upgrade to account for said change. Soon after, if any of the PoW miners fail to upgrade their clients accordingly, the blocks packaged by the miners will not be accepted by the supernodes. In this way, the majority of the power is given to the Cyber Republic community rather than the miners themselves, which prevents forks from occuring in the first place.