In Epoch, some randomness is often needed, such as the genes of NFT, randomly selecting the winners, etc. In this case, the randomness of the number of periods is not necessary. In this case, the security of the random number is crucial, it cannot be predicted or manipulated. Before EMIT Core went online, we generated this randomness through Period Service contracts. The Super Node generates a Seed at the end of each Period through the Period Service, which has the following characteristics: before the Seed is announced, no one can guess the actual data of the Seed, and after the Seed is announced, it only affects the transactions from before the Seed has been announced. The randomness of access to the exchange is determined by the Seed and the transaction itself. A Period is set to 24 hours.