Uniform Randomization for Block Double Validation

Abstract

TomoChain1 is a blockchain based on Ethereum framework with the following advantages points: low transaction fee, fast confirmation time, double validation and randomization for security guarantees. In our previous technical white paper, we proposed Proof-of-Stake Voting (PoSV) consensus protocol, a Proof-of-Stake (PoS)-based blockchain protocol with a fair voting mechanism, rigorous security guarantees and fast finality. One of the key parts of PoSV is the double validation process, which requires randomization to generate the list of block verifiers (with uniform distribution and unpredictability) for each epoch. In other words, randomization of block verifiers in double validation is the key factor of reducing risks coming from paired hand-shaking attackers trying to commit malicious blocks. In this paper, we focus on studying methods for randomization of block verifiers. In particular, we study combinatorial and probability theory, and then apply the fixed-point-free permutation method for randomization. With this approach, we show that the contributions and benefits of verifiers are fair in the sense that the probability distribution function is uniform eventually. Finally, we implement the proposed protocol and conduct experiments on TomoChain public blockchain.