Security is one of the most important considerations when writing smart contracts. In the field of smart contract programming, mistakes are costly and easily exploited. In this chapter we will look at security best practices and design patterns, as well as “security antipatterns,” which are practices and patterns that can introduce vulnerabilities in our smart contracts.
As with other programs, a smart contract will execute exactly what is written, which is not always what the programmer intended. Furthermore, all smart contracts are public, and any user can interact with them simply by creating a transaction. Any vulnerability can be exploited, and losses are almost always impossible to recover. It is therefore critical to follow best practices and use well-tested design patterns.