Smart contract is one of the core technologies of blockchain,and its security and reliability are very important. With the popularization of blockchain application,the number of smart contracts has increased explosively. And the vulnerabilities of smart contracts will bring huge losses to users. However,the current research focuses on the semantic analysis of Ethereum smart contracts,the modeling and optimization of symbolic execution,and does not specifically describe the process of detecting smart contract vulnerabilities using symbolic execution technology,and how to detect common vulnerabilities in smart contracts. Based on the analysis of the operation mechanism and common vulnerabilities of Ethereum smart contract,the symbol execution technology was used to detect vulnerabilities in smart contracts. Firstly,the smart contract control flow graph was constructed based on Ethereum bytecode,then the corresponding constraint conditions were designed according to the characteristics of smart contract vulnerabilities,and the constraint solver was used to generate software test cases to detect the common vulnerabilities of smart contracts such as integer overflow,access control,call injection and reentry attack. The experimental results show that the proposed detection scheme has good detection effect, and has the accuracy of smart contract vulnerability detection up to 85% on 70 smart contracts with vulnerabilities in Awesome-Buggy-ERC20-Tokens.

Most Radio Frequency Identification (RFID) tag anti-collision protocols have the problem that too many bits are transmitted by tag during the identification. To solve this issue, an Enhanced Multi-Bit Identification (EnMBI) algorithm was proposed. On the premise of guaranteeing the identification efficiency, a frame-slotted structure was adopted to avoid the repeated transmitting of common prefixes. Meanwhile, through locating the collision bits, only the collision bits were recovered so as to further decrease the communication overhead. The simulation results show that the EnMBI algorithm has less tag overhead and total overhead than the multi-bit identification anti-collision algorithm. Its total overhead is at most 20% lower than the multi-bit identification algorithm.