# Hybrid Consensus Algorithm Based on Modified Proof-of-Probability and DPoS
## 5 Evaluation and Results
### Scalability
Although the competition of computing power is avoided and the system efficiency is improved, they have almost all the power (i.e., the power of block generation and verification), which to a certain extent, sacrifices decentralization and is easy to form a new monopoly. Thus, by combining PoP and DPoS, we can not only compete for bookkeeping rights fairly through proper mining, but also weaken the power of DPoS supernodes (i.e., the power to generate blocks is handed over to PoP nodes), and only block verification can be carried out through them. Block verification by a small number of nodes inherits the high efficiency of DPoS to a certain extent, and effectively avoids the occurrence of monopoly. Therefore, the proposed consensus algorithm can provide good decentralization for the blockchain system. Scalability: In the blockchain system based on the PoW algorithm, the throughput usually decreases with the increase in the number of nodes. As time goes on, excessive computing power competition will lead to the increasing difficulty of target hash calculation, and it will take more time for the system to reach a consensus due to the increase in the number of nodes. In contrast, the proposed algorithm has a relatively low throughput only when the number of supernodes is small, which leads to the increase in election times. With the increase in the number of nodes, its throughput will gradually improve and tend to be stable. Due to block verification being only carried out by a small number of DPoS supernodes, it takes less time for the blockchain system to reach a consensus, that is, the throughput of the algorithm is not easily affected by the number of nodes. Therefore, with the same number of nodes, the throughput of the proposed algorithm is basically higher than that of the PoW algorithm. Punishment mechanism: In the blockchain system represented by bitcoin, there is usually no good supervision and punishment mechanism, which means malicious nodes will not be punished even if they carry out malicious attacks, which obviously increases the security risk of the blockchain system. In the proposed algorithm, DPoS supernodes are still monitored by other DPoS nodes after being elected. Once a supernode is found to have malicious behavior, other nodes will vote to remove the supernode from the system. In addition, the algorithm also provides a similar punishment mechanism for PoP nodes. Once a PoP node has malicious behavior, it will be immediately removed by voting. Therefore, the proposed algorithm has a basic punishment mechanism. Resistance to temporary fork: In most blockchain systems such as the bitcoin system, once two nodes generate blocks at the same time, it will generally cause a short-term blockchain fork. Other nodes will continue mining on the first received blockchain until one blockchain is longer than the other, and the short blockchain will be replaced. In the proposed algorithm, the method to deal with fork is the same as bitcoin. The difference is that our algorithm makes it more difficult for blockchain system to fork than the bitcoin system. In our blockchain system, when a node generates a block, it needs to further meet the expected value before it can pass block verification. The minimum success rate is 10% and the average success rate is 55%. Therefore, when two nodes generate blocks at the same time, they also need to meet the expected value before fork occurs. By calculation, we can see that the minimum success rate is 1%, and the average success rate is 30.25%. Therefore, the proposed algorithm can make the blockchain system much more difficult to fork than the general blockchain system. Resistance to various attacks:  
1. 51% attack: For the blockchain system based on a single consensus algorithm, malicious nodes usually only need 51% of the computing power or 51% of the token in the system to launch 51% attacks.