Building an NFT wallet app – implementation

In the previous post in this series, I have presented a simple architecture for an NFT wallet app, written in ReactJS. Today, I will dive a bit deeper into the implementation. The source code for this post can be found here. As most of it is fairly standard ReactJS code, I will not discuss all…More

Building an NFT wallet app – architecture

In the last two posts, we have installed geth and implemented our NFT contract in Solidity according to the ERC-721 standard. Today, we will start to dive into the implementation of a React front-end serving as a simple wallet for our NFT. Overall architecture and components First, let us pause for a moment and think…More

Running and using Go-Ethereum

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