Mainstay: A hybrid protocol ensuring ledger temporality and security

To enhance the scalability of blockchain ledger structure, researchers have abandoned the traditional single-chain structure and used the structure of Directed Acyclic Graph (DAG) to achieve high-concurrency processing of transactions. The DAG-based ledger requires a specific topological structure and block sorting rules to ensure the temporality and security of the ledger structure. This paper proposes a hybrid protocol called Mainstay with a double-layer structure, including the DAG-Ledger layer and the NC-Chain layer. The DAG-Ledger layer uses PHANTOM structure to confirm the transaction block order; the NC-Chain uses dynamic committee elections, voting, and fast verification to form a blockchain similar to the Nakamoto style, and each block of the NC-Chain requires committee members to calculate the Verifiable Delay Function (VDF) to generate a quorum certificate(QC), which can ensure the stability and security of the DAG-Ledger layer ledger sequence. By experimental comparison, we conclude that the Mainstay protocol can effectively reduce the probability of malicious attackers successfully attacking the ledger structure.