Most of the time, we have been using the Brownie development environment for our tests so far, and with it the Ganache Ethereum client that Brownie runs behind the scenes. For some applications, it is useful to have other clients at our disposal. The Go-Ethereum client (geth) is the most commonly used client at the…More
Implementing and testing an ERC721 contract
In the previous posts, we have discussed the ERC721 standard and how metadata and the actual asset behind a token are stored. With this, we have all the ingredients in place to tackle the actual implementation. Today, I will show you how an NFT contract can be implemented in Solidity and how to deploy and…More
Using NFT metadata to safely store digital assets
If you read about NFTs for the first time, you might be under the impression that an NFT somehow stores a digital asset in the blockchain. In most of the cases, however, this is not true. If you have read my previous post, you will remember that in its essence, an NFT is nothing but…More
Non-fungible token (NFT) and the ERC-721 standard
NFTs (non-fungible token) are one of the latest and most exciting developments in the blockchain universe, with use cases ranging from such essential things as breeding cute virtual kitten digitally on the blockchain to digital auctions as conducted earlier this year by the renowned fine art auctioneer Sothebys’s. In this post, we will explain why…More
Reconstructing the August 27th attack on the Ethereum blockchain
On August 27th 2021, a malicious transaction was created on the Ethereum mainnet, targeting a vulnerability in all versions of Go-Ethereum up to 1.10.7. If successful, this could have resulted in a fork of the production network. Fortunately, this could be avoided as a sufficient number of nodes were already running version 1.10.8 of Go-Ethereum…More
Understanding the Ethereum virtual machine – part III
Having found our way through the mechanics of the Ethereum virtual machine in the last post, we are now in a position to better understand what exactly goes on when a smart contracts hand over control to another smart contract or transfers Ether. Calls and static calls Towards the end of the previous post in…More
Understanding the Ethereum virtual machine – part II
In todays post, we will complete our understanding of how the EVM executes a smart contract. We will investigate the actual interpreter loop, discuss gas handling and have a short look at pre-compiled contracts. The jump table and the main loop In the last post, we have seen that the entry point to the actual…More
Understanding the Ethereum virtual machine – part I
In todays post, we will shed some light on how the Ethereum virtual machine (EVM) actually works under the hood. We start with an overview of the most relevant data structures and methods and explain the big picture before we look at the interpreter main loop in the next post. The Go-Ethereum EVM – an…More
A deep-dive into Solidity – function selectors, encoding and state variables
In the last post, we have seen how the Solidity compiler creates code – the init bytecode – to prepare and deploy the actual bytecode executed at runtime. Today, we will look at a few standard patterns that we find when looking at this runtime bytecode. Some useful tools While analyzing the init bytecode in…More
A deep-dive into Solidity – contract creation and the init code
In some of the previous posts in this series, we have already touched upon contract creation and referred to the fact that during contract creation, an init bytecode is sent as part of a transaction which is supposed to return the actual bytecode of the smart contract. In this and the next post, we will…More
LeftAsExercise 