Mastering Ethereum, 2nd Edition

Chapter 9. Smart Contract Security

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 into 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.

Think of robust development as the first layer in a “Swiss cheese model” of security. Each layer of protection acts like a slice of Swiss cheese: none is flawless on its own, but together they create a stronger defense. The very first layer is following solid development practices: using reliable design patterns, writing clear and intentional code, and actively avoiding known pitfalls. This foundational layer gives us the best start in securing our contracts from vulnerabilities. Beyond this, other layers like testing, code reviews, and bug bounties add extra protection, but it all begins with our development practices.

Security Best Practices

Defensive programming is ...