Research And Applications Of Blockchain Security Technology

With the rapid development of information technology,network security and privacy preserving have been paid increasing attention.The traditional way to solve these problems is to design complex cryptographic protocols to enhance security.However,the traditional solution is based on a centralized system.The more powerful the system center is,the more vulnerable it is to attackers.Bitcoin was the earliest application of blockchain technology.Nakamoto Satoshi designed a proof of work mechanism to ensure the security of asset transfer in decentralized system.In an untrusted network environment,a blockchain system that employs a proof-of-work mechanism can complete the distribution and transfer of digital assets.The blockchain consensus is based on a set of economic incentives and penalties.In the system,different consensus mechanisms can be used to achieve different security.Among them,the proof of workload is still the most secure consensus mechanism in the blockchain,and the different mining algorithms used on this basis are the necessary means to protect the new blockchain against 51% attacks.In order to guarantee the security of the blockchain and prevent the computational power from being concentrated on a certain number of nodes and from 51% of the computational power,it is necessary to disperse the computing power to ordinary users as much as possible.This requires increasing the proportion of mining for common users and lowering the threshold for mining.Each user has CPU and GPU resources.If the mining algorithm is CPU-and GPU-friendly,then the proportion of common users mining can be increased to some extent.Although the ASIC mining machine has high mining efficiency,ordinary users have a certain threshold for mining.In order to inhibit the addition of ASIC mining machines,it is necessary to improve the use of memory resources in algorithm design.Because in the ASIC mining machine,there is a certain limit to the access to the memory,the speed of the hardware circuit to access the memory resources is strictly limited,so the algorithm that requires higher memory resources is not suitable for designing a professional ASIC mining machine.This provides an idea for the design of the mining algorithm.That is,by increasing the memory resource requirements of the mining algorithm,it can decentralize the computing power to a certain extent,thereby reducing the possibility of 51% attack and ensuring the blockchain security.At the same time,Ethereum smart contracts provide a scalable application platform for blockchains based on the security and stability of the system.The decentralized application running on Ethereum smart contracts can secure stable operation without trusting the network environment.The high security of decentralized applications has led people to pay more and more attention to its enormous development potential.Based on the above points,this thesis introduces the following contributions:1.Based on the traditional merkle tree,a mining algorithm based on the Merkle tree is presented.The scheme first generates a random number set according to certain rules and generates a Merkle tree.After that,a node is arbitrarily selected at each level of the Merkle tree,and finally all the nodes are connected to do a hash operation.The entire algorithmic process consumes a large amount of memory resources,which is consistent with the requirement that the mining algorithm in the blockchain requires computer resources.Moreover,because the mining algorithm occupies more system memory,it can increase the design difficulty of the ASIC mining machine to some extent,and alleviate the centralization problem of mining and mining power.2.Based on the traditional Bloom filter,a workload verification mining algorithm based on Bloom filter is proposed.The scheme first generates a set of random numbers according to certain rules and sequentially fills the array of bloom filters with the hash function of the Bloom filter.Then calculate the sum of the values of the first array element and one of the other array elements.This scheme needs to consume a large amount of memory resources during the calculation of the bloom filter,which meets the requirement of the blockchain mining algorithm to occupy computer resources.3.Based on the Ethereum smart contract,a notarization certificate is issued.Traditional public key certificate issuance is always accompanied by an attacker attacking the channel and certificate issuing authority.With the use of Ethereum smart contracts to issue public key certificates,both users and certificate authorities can bypass traditional channels.At the same time,Ethereum's highly secure consensus mechanism ensures that attack costs are very high.