• Zeppelin

    Openzeppelin Contracts v4 in Review

    Taking a look at the new Openzeppelin v4 Release

    The Openzeppelin v4 contracts are now available in Beta and most notably come with Solidity 0.8 support. For older compiler versions, you'll need to stick with the older contract versions. The beta tag means there still might be small breaking changes coming for the final v4 version, but you can...

  • Loan

    EIP-3156: Creating a standard for Flash Loans

    A new standard for flash loans unifying the interface + wrappers for existing ecosystems

    As we've discussed last week, flash loans are a commonly used pattern for hacks. But what exactly are they and how are they implemented in the contracts? As of right now each protocol has its own way of implementing flash loans. With EIP-3156 we will get a standardized interface. The standard was...

  • Zero

    Tornado.cash: A story of anonymity and zk-SNARKs

    What is Tornado.cash, how to use it and the future

    With the recent Yearn vault v1 hack from just a few days ago, we can see a new pattern of hacks emerging: Get anonymous ETH via tornado.cash . Use the ETH to pay for the hack transaction(s). Use a flash loan to decrease capital requirements. Create some imbalances given the large capital and...

  • Roulette Game

    High Stakes Roulette on Ethereum

    Learn by Example: Building a secure High Stakes Roulette

    It's always best to learn with examples. So let's build a little online casino on the blockchain. We'll also make it secure enough to allow playing in really high stakes by adding a secure randomness generator. Let's discuss the overall design first. Designing the contract Before we program...

  • Meta Transaction

    How to implement generalized meta transactions

    We'll explore a powerful design for meta transactions based on 0x

    Enabling meta transactions inside your contract is a powerful addition. Requiring users to hold ETH to pay for gas has always been and still is one of the biggest user onboarding challenges. Who knows how many more people would be using Ethereum right now if it was just a simple click? But...

  • Map

    Utilizing Bitmaps to dramatically save on Gas

    A simple pattern which can save you a lot of money

    As you may know the most expensive operation in Ethereum is storing data ( SSTORE ). So you should always look for ways to reduce the storage requirements. Let's explore a particularly useful one: Bitmaps. How to implement a simple Bitmap Let's assume we want to store 10 boolean values. Usually...

  • Uniswap

    Using the new Uniswap v2 as oracle in your contracts

    How does the Uniswap v2 oracle function and how to integrate with it

    We've covered Uniswap previously here . But let's go through the basics first again. What is UniSwap? If you're not familiar with Uniswap yet, it's a fully decentralized protocol for automated liquidity provision on Ethereum. An easier-to-understand description would be that it's a decentralized...

  • People making fun

    Smock: The powerful mocking tool for Hardhat

    Features of smock and how to use them with examples

    We’ve covered mocking contracts before , but now there’s an additional great tool available: smock . It simplifies the mocking process greatly and also gives you more testing power. You’ll be able to change the return values for functions as well as changing internal contract storage directly!...

  • 721 Insurance

    How to build and use ERC-721 tokens in 2021

    An intro for devs to the uniquely identifying token standard and its future

    The ERC-721 standard has been around for a while now. Originally made popular by blockchain games, it's more and more used for other applications like Defi. But what exactly is it? A non-fungible token (NFT) is a uniquely identifying token. The word non-fungible implies you cannot just replace...

  • Set Protocol

    Trustless token management with Set Protocol

    How to integrate token sets in your contracts

    With Set Protocol you can create baskets of tokens that give users different levels of exposure to underlying assets (currently only ERC-20 tokens). Set Protocol and their TokenSet functionality is the perfect example for making use of the new paradigm of Defi and composability. You can let...

  • Solidity 0.8

    Exploring the new Solidity 0.8 Release

    And how to upgrade your contracts to Solidity 0.8

    We are getting closer to that Solidity 1.0 release (unless of course after 0.9 comes 0.10). Now Solidity 0.8 has been released only 5 months after the 0.7 release ! Let's explore how you can migrate your contracts today... New features & how to use them Let's look at the two big new features...

  • Multi Currency

    How to build and use ERC-1155 tokens

    An intro to the new standard for having many tokens in one

    ERC-1155 allows you to send multiple different token classes in one transactions. You can imagine it as transferring Chinese Yuan and US Dollars in a single transfer. ERC-1155 is most commonly known for being used in games, but there are many more use cases for it. First of all though, what are...

  • RSK

    Leveraging the power of Bitcoins with RSK

    Learn how RSK works and how to deploy your smart contracts to it

    I'm always interested in what other ways one can use their blockchain and Solidity skills. While many projects are still only in the planning or in testnet status, with Rootstock (RSK) you can transfer mainnet Bitcoins to an EVM sidechain and vice-versa already today. Utilizing the power of the...

  • Solidity Overview

    Solidity Fast Track: Learn Solidity Fast

    'Learn X in Y minutes' this time with X = Solidity 0.7 and Y = 20

    You might be familiar with the Learn X in Y minutes. For example you could learn JavaScript in 20 minutes at https://learnxinyminutes.com/docs/javascript/ . Unfortunately there is no equivalent for Solidity, but this is about to change. Do you have 20 minutes to learn all of the basics? We even...