By Ultrain’s Chief Cryptologist Husen Wang
RPoS Consensus is divided into the following stages
1、There are two committees, C1 and C2. Both can be joined freely with deposited stakes.
2、C1 periodically generates a random number r using Verifiable Random Function. Proposers and Voters are selected by the Fisher-Yates shuffle algorithm with priorities.
3、All proposers initiate their blocks, where all voters verify and vote upon the highest priority proposer’s block. The votes are signed with aggregatable signature. This makes lightweight client and cross chain transaction verification possible.
4、After collecting enough votes through BFT algorithm, all nodes generate its block independently, and the corresponding proposer gets rewarded.
Compared with DPoS
1、RPoS is more decentralized and safe. Since DPoS has limited amount of nodes, it leaves room for “under the table” collusion between nodes, which compromises the overall security and fairness of the network. For example, during the random number generation process, fairness is required. However, nodes in DPoS can collude to predict or manipulate future random number without being detected.
2、With larger amount of nodes, RPoS is harder to be attacked when compared with DPoS~There are a limited number of nodes in DPoS, thus easier to be attacked, which results in the overall failure of the network or a fork.
Compared with Dfinity:
1、The BLS signature of Dfinity needs to assume security in Gap Diﬃe-Hellman (GDH) group , which might limit the security level of randomness. Threshold signature requires pairing calculation that runs slowly. During the process of threshold signature, members need to exchange information, which may result in a slow threshold signature and increase vulnerability to malicious attack. RPoS limits threshold signature to voting and changes voters frequently without group setup problem.
2、If participants can join and exit freely the group, it may lead to stolen of private key and predictable randomness.
3、The signature of groups cannot be compared to that of the PoW system (such as bitcoin), thus the security of block confirmation cannot be guaranteed and results in a longer confirmation time.
Compared with Algorand:
1、Algorand selects its committee member, especially the proposers, based on probability. Which might result in multiple proposers that causes the issue of “network storm”, which increases the overall consumption of bandwidth for nodes.
2、RPoS utilizes threshold signature algorithm, which composes a smaller voter message that is easy to transmit within the network and for client side verification.
3、RPoS introduces an incentive mechanism for both proposer and voter, a double signature punishment system that further improves overall security.
1、RPoS optimizes layer0 message transmission, to minimizes arrival time for message propagation.
2、The RPoS plans to introduce TEE and KYC mechanism to further improve the overall system security.