You are presented with multiple paper abstracts, alongside the associated literature review and chapter titles. Given the provided information, you are going to do a literature review. Please generate a coherent literature review that synthesizes the content, draws connections between different works, highlights major findings, and identifies any gaps in the existing research.

Literature Review Title: A Survey on Security Verification of Blockchain Smart Contracts 
Chapter Title:  1) BLOCKCHAIN SECURITY 
1. Abstract of Cited Paper (BIB001):  Since its inception, the blockchain technology has shown promising application prospects. From the initial cryptocurrency to the current smart contract, blockchain has been applied to many fields. Although there are some studies on the security and privacy issues of blockchain, there lacks a systematic examination on the security of blockchain systems. In this paper, we conduct a systematic study on the security threats to blockchain and survey the corresponding real attacks by examining popular blockchain systems. We also review the security enhancement solutions for blockchain, which could be used in the development of various blockchain systems, and suggest some future directions to stir research efforts into this area.

Literature Review:
Several studies summarized common problems in blockchain security and depicted a macro blueprint for building a secure and reliable execution environment. Alharby and Moorsel BIB001 pointed out that the common risks in the blockchain including 51% of computing power, private key protection, criminal activities, double payment, and transaction information disclosure, etc. By analyzing the causes of the problems they provided some existing solutions. Li et al. BIB002 studied the execution process of smart contracts in the blockchain, and proposed two issues of transaction order dependency and timestamp dependency. The transaction was not executed in the correct order or the miner maliciously modified the block timestamp may affect the correctness of the smart contract. Simultaneously they suggested that using the OYENTE tool to detect smart contracts was a perfect solution.