| Blockchain technology is an integrated application of cutting-edge theories such as block chain storage,distributed consensus protocols,cryptography,and game theory.It has the characteristics of decentralization,tamper-proof,and traceability.The consensus protocol specifies how the nodes of the entire blockchain network can reach consensus on data in a non-trusted environment,and its security and performance directly determine the availability of the blockchain.However,due to the imperfect design of various consensus protocols,the consensus layer of the blockchain faces various security issues such as 51%double-spend attacks,selfish mining attacks,and DoS attacks against fragmented consensus.Aiming at the 51%attack problem in the Proof-Of-Work(PoW)consensus protocol,this paper studies the improvement scheme of the protocol,and proposes a PoW consensus technology based on the characteristics of the node’s historical block generation,which increases the attacker’s continuous generation area.The difficulty of the block improves the protocol’s defense against 51%attacks.Aiming at the problem that the single-shard DoS attack in the sharding consensus affects the system availability,this paper studies the characteristics and protection of the attack,and proposes a shard transaction division technology based on a verifiable random function,which realizes the random division of transactions and solves the problem of Single-shard DoS attack.The work content and research results of this paper mainly include:(1)In view of the existing PoW consensus protocol,the attacker initiates a 51%attack by renting computing power and other methods to cause double-spending of tokens.The difficulty of block generation and the introduction of contribution to guide nodes to actively participate in the consensus have improved the protocol’s defense against 51%attacks.(2)Aiming at the single shard DoS attack problem faced by the hashbased transaction division method in the sharding consensus,this paper proposes a shard transaction division technology based on a verifiable random function,which realizes transactions to shards in a random and unpredictable way.The experimental results show that when the proportion of malicious transactions is high,the impact of attacks on system performance can be significantly reduced.(3)Design and implement the blockchain multi-shard consensus system.The system has added the two consensus technologies proposed in this paper on the basis of the basic functions of the sharded blockchain,and applied them to the division of shard members and transactions of the system respectively.In the division module,the correctness and completeness of the system’s membership division,transaction request consensus and other functions are tested. |
