With the rapid development of Internet of Things （IoT） and industrial Internet， the research of cyberspace security has been paid more and more attention by industry and academia. Because the source code cannot be obtained， binary code similarity search has become a key core technology for vulnerability mining and malware code analysis. Firstly， the basic concepts of binary code similarity search and the framework of binary code similarity search system were introduced. Secondly， the development status of binary code technology about syntax similarity search， semantic similarity search and pragmatic similarity search were discussed. Then， the existing solutions were summarized and compared from the perspectives of binary hash， instruction sequence， graph structure， basic block semantics， feature learning， debugging information recovery and advanced semantic recognition of functions. Finally， the future development direction and prospect of binary code similarity search were looked forward to.

Focused on the issue that the CKKS (Cheon-Kim-Kim-Song) homomorphic encryption scheme based on the Learning With Errors (LWE) problem has large ciphertext, complicated calculation key generation and low homomorphic calculation efficiency in the encrypted data calculation, an optimized scheme of LWE type CKKS was proposed through the method of bit discarding and homomorphic calculation key reorganization. Firstly, the size of the ciphertext in the homomorphic multiplication process was reduced by discarding part of the low-order bits of the ciphertext vector and part of the low-order bits of the ciphertext tensor product in the homomorphic multiplication. Secondly, the method of bit discarding was used to reorganize and optimize the homomorphic calculation key, so as to remove the irrelevant extension items in powersof2 during the key exchange procedure and reduce the scale of the calculation key as well as the noise increase in the process of homomorphic multiplication. On the basis of ensuring the security of the original scheme, the proposed optimized scheme makes the dimension of the calculation key reduced, and the computational complexity of the homomorphic multiplication reduced. The analysis results show that the proposed optimized scheme reduces the computational complexity of the homomorphic calculation and calculation key generation process to a certain extent, so as to reduce the storage overhead and improve the efficiency of the homomorphic multiplication operation.