The future of a Decentralized Etherscan
Learn how to use the new Sourcify infrastructure today
We all love Etherscan. It's a great tool to interact with contracts, read the source codes or just see the status of your transactions. But unfortunately as great as it is, we should not forget that it's a centralized service. The website could be taken down any day. This kind of defeats the purpose of using decentralized infrastructure in the first place.
But there is no reason for why we need to rely only on this centralized service. All functions can be done in a decentralized way. Some already today, some will come in the future.
Let's explore how...
The problems solved by Etherscan
- Source Code Availability
- Interaction via ABI
- Transaction Status
Problem 1: Source Code Availability
We want a contract to have a verified source code. Without the source code, we can only see the contract bytecode. While there are decompilers (one even added to Etherscan), they are far, far away from having the actual source code. For trustability users need to be able to verify the source code. Until now this is generally done via Etherscan verifications. Most tools support the verification in this way and it has become the de facto standard way.
This is also the biggest problem with Etherscan. If the site gets taken down, all source code information is lost. Then we have thousands of contracts that we need to trust blindly if we want to use them.
Problem 2: Interaction via ABI
This one goes hand in hand with the first problem, but it's a separate issue on its own. Without having the contract's ABI, we cannot interact with it properly. Once again, to some degree it's possible to recover an ABI just from the bytecode, but not always or only partially. This is due to the function signatures being the last 4 bytes of the function name + arguments. So if you don't know the function names and arguments, you can't create a proper ABI.
Problem 3: Transaction Status
People also use Etherscan to look at the current transaction status. It goes as far as MetaMask directly linking to Etherscan for the status. But we are once again relying on a centralized service here. While MetaMask is using Infura for transaction confirmation notifications, even Infura is a centralized service and has been down just three days ago. There are further centralized services like Blocknative for more advanced transaction status tracking.
There is no reason why all of this infrastructure must be designed in a centralized way. We can do better!
Solving Problem 1 and 2: Sourcify - A Decentralized Alternative
Sourcify has been been a recent collective to build alternatives. There's a great FAQ available here. At its heart Sourcify is a decentralized register for contract metadata. You can browse the register here. By providing this register it sets the foundation for a new infrastructure and tooling around it. You can expect the use of Sourcify to become much more widespread in the future.
Let's take a look how this is achieved.
A. What is the Metadata?
First of all, what is the metadata of a contract? The metadata is not new. I went back to the documentation and the first mention of it dates back to v0.4.7 which was back in December 2016. The latest documentation about it can be seen here.
The metadata contains all the information to securely interact with this contract. And this is actually more than Etherscan verification is providing. It contains
- compiler settings
- source code
- ABI
- all code documentation like Natspec and inline comments
While you get the first three with Etherscan, you have absolutely no guarantee that the comments and Natspec documentation matches the one used at deployment time. You would think, how could it? It's just a comment and doesn't affect the code after all.
That's true. But as it turns out the metadata is actually appended to a contract's bytecode on deployment and Etherscan just ignores this. This makes sense for a service like Etherscan as the metadata can differ for various reasons and it would be very difficult (even more than it already is) to verify a contract successfully on Etherscan.
So as it turns out, the code comments could be very different (even malicious) and whoever verifies a contract on Etherscan first is chosen as the correct result.
B. Let's use IPFS to store the Metadata
Now that we know how powerful the metadata file is we 'only' need a way to distribute it securely. It's been 4 years since the metadata exists and yet we only now are starting to find a solution. Can someone explain how this took so long?
If you're not familiar with IPFS yet, check out my previous tutorial on it here. In short for now, it's a decentralized storage service. So it's perfect for our use case of storing the metadata along with the source code files.
Let's look at one example:
Under https://repo.sourcify.dev/contracts/full_match/4/0xA67e9490da7899Dd400973190Ba952557AbE92eF/ you can find the published metadata file and source code. The metadata file contains also the IPFS hash for the source files. You could browse those directly, for example in our example under https://ipfs.io/ipfs/QmdFKz1mJcE8MCfeRnkmEaJ2oF62LAmjxbbrLqzxvAXBTb would be the main source file.
This has been the intended use case for the metadata and is already explained in the docs here. Now there is one major issue with IPFS and that is keeping those files online. Sourcify will ensure this using IPFS pinning.
C. How to publish your contracts via Sourcify
Conceptually Sourcify has two ways to verify a contract.
- Upload the metadata file for a deployed contract.
- Publish the metadata to IPFS before deployment. A monitor service automatically checks if any new deployments match an existing metadata file.
(I) Manually
Your first option is to just manually upload the metadata file under https://sourcify.dev/. A tool like this is required to be able to add metadata files for already deployed contracts.
Note that you don't have to use the UI, but you can also use the Remix plugin (or CLI which will be released in the future). For details on this see the Remix section below.
(II) Remix
Remix has wide support for metadata uploads.
- You can activate the Sourcify plugin. The plugin section is the icon on the bottom. Once activated you will see a screen as shown on the right. The plugin allows you to verify and fetch contract metadata. In particular the fetch will be useful in the future. Want to interact with a contract? Just fetch the data here in Remix and you will get the full source code including all comments and ABI.
- We can also use the second way of publishing the metadata pre-deployment. You can either choose to publish to IPFS in the compile tab:
Or most conveniently, just activate the option on deployments.
(III) Truffle
In Truffle the metadata is already created for you. There is no direct support for publishing on IPFS yet, but there's a simple example available here.
And on the right is the example code for uploading metadata files to IPFS inside a Truffle project. As you can see, the metadata can be found in ./build/contracts/MyContractName.json and then under .metadata.
Once we have this data, we can use IPFS (in this case connected to an Infura node) and upload the metadata and source files. In this script we automatically go through all compiled Truffle contracts and upload all relevant metadata and source files.
Now all you have to do is make sure to run this command before the deployment. This will ensure the Sourcify monitor will automatically match the new deployment when it's written to the chain.
const IPFS = require('ipfs-http-client');
const shell = require('shelljs');
const path = require('path');
async function uploadToIPFS(){
const host = 'ipfs.infura.io';
const ipfs = IPFS({ host, port: '5001', protocol: 'https' });
const artifactPaths = shell.ls('./build/contracts/*.json');
for (let _path of artifactPaths){
const artifact = require(path.join(process.cwd(), _path));
console.log(artifact.contractName);
for await (const res of ipfs.add(artifact.metadata)) {
console.log(`metadata: ${res.path}`);
}
for await (const res of ipfs.add(artifact.source)) {
console.log(`source: ${res.path}`);
}
}
}(IV) Hardhat (ex Buidler)
Likewise in Hardhat there is no direct Sourcify support yet. But with the hardhat-deploy plugin, the metadata is already created for you. Unless you change the configuration, you will find the metadata under ./deployments/{networkName}/MyContract.json and then again under .metadata. You can use an upload script to IPFS as shown above.
Or you can wait for better upload support as the hardhat-deploy plugin has this already on their TODO list here.
Going beyond Etherscan
What we've discussed so far is the most pressing issue and likely the first becoming used more.
But we can even go one or actually two steps further.
Integration into wallets
The metadata adds further support for Natspec as explained here. This is good news as Natspec is already widely used for Solidity contracts. Usually as pure developer documentation, the Natspec could now also be used as user documentation.
Remember the last time you confirmed a transaction?
Did it look anything like shown on the right?
Yeah, we all now exactly what this transaction will be doing. This is where the Natspec can come in. Instead of this dialogue, a user might get a description such as
'Swap 100 ETH for at least 45,000 DAI if the trade is executed within the next 100 seconds.'
Now this is quite a bit more readable than the hex data, isn't it?
Transaction Status and Mempools
A few of the issues to solve here are
- How can you reliably find out the transaction status?
- How can you properly ensure a transaction is actually mined?
- Is there a way to prevent front-running?
Unfortunately Sourcify won't help with this issue. We will have to wait for something else. But I feel optimistic that a solution process can at least be started within the next few years.
Decentralization: One step at a time
As you might have noticed, a lot of the architecture is still very much work in progress. I also feel like we will need a few websites that allow for easy interaction with contracts that have published metadata. Remix is a good start, but make it even simpler. Kind of like the Etherscan Dapp pages, but utilizing Sourcify.
This is a great hackathon project in case you need are in need for a project idea. ;)
If you have not seen the original posts about Sourcify by the main guy behind Solidity, Christian Reitwiessner aka chriseth, check them out here:
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What is the EXTCODEHASH? The EVM opcode EXTCODEHASH was added on February 28, 2019 via EIP-1052. Not only does it help to reduce external function calls for compiled Solidity contracts, it also adds additional functionality. It gives you the hash of the code from an address. Since only contract...
Using the new Uniswap v2 in your contracts
What's new in Uniswap v2 and how to integrate Uniswap v2
Note : For Uniswap 3 check out the tutorial here. 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 exchange (DEX) relying on external...
Solidity and Truffle Continuous Integration Setup
How to setup Travis or Circle CI for Truffle testing along with useful plugins.
Continuous integration (CI) with Truffle is great for developing once you have a basic set of tests implemented. It allows you to run very long tests, ensure all tests pass before merging a pull request and to keep track of various statistics using additional tools. We will use the Truffle...
Upcoming Devcon 2021 and other events
The Ethereum Foundation just announced the next Devcon in 2021 in Colombia
Biggest virtual hackathon almost finished First of all, the current HackMoney event has come to an end and it has been a massive success. One can only imagine what kind of cool projects people have built in a 30 days hackathon. All final projects can be seen at:...
The Year of the 20: Creating an ERC20 in 2020
How to use the latest and best tools to create an ERC-20 token contract
You know what an ERC-20 is, you probably have created your own versions of it several times (if not, have a look at: ERC-20). But how would you start in 2020 using the latest tools? Let's create a new ERC-2020 token contract with some basic functionality which focuses on simplicity and latest...
How to get a Solidity developer job?
There are many ways to get a Solidity job and it might be easier than you think!
You have mastered the basics of Solidity, created your first few useful projects and now want to get your hands on some real-world projects. Getting a Solidity developer job might be easier than you think. There are generally plenty of options to choose from and often times not a lot of...
Design Pattern Solidity: Mock contracts for testing
Why you should make fun of your contracts
Mock objects are a common design pattern in object-oriented programming. Coming from the old French word 'mocquer' with the meaning of 'making fun of', it evolved to 'imitating something real' which is actually what we are doing in programming. Please only make fun of your smart contracts if you...
Kickstart your Dapp frontend development with create-eth-app
An overview on how to use the app and its features
Last time we looked at the big picture of Solidity and already mentioned the create-eth-app. Now you will find out how to use it, what features are integrated and additional ideas on how to expand on it. Started by Paul Razvan Berg, the founder of sablier, this app will kickstart your frontend...
The big picture of Solidity and Blockchain development in 2020
Overview of the most important technologies, services and tools that you need to know
Now, I do not know about you, but I remember when I first started with Solidity development being very confused by all the tools and services and how they work in connection with one another. If you are like me, this overview will help you understand the big picture of Solidity development. As I...
Design Pattern Solidity: Free up unused storage
Why you should clean up after yourself
You may or may not be used to a garbage collectors in your previous programming language. There is no such thing in Solidity and even if there was a similar concept, you would still be better off managing state data yourself. Only you as a programmer can know exactly which data will not be used...
How to setup Solidity Developer Environment on Windows
What you need to know about developing on Windows
Using Windows for development, especially for Solidity development, can be a pain sometimes, but it does not have to be. Once you have configured your environment properly, it can actually be extremely efficient and Windows is a very, very stable OS, so your overall experience can be amazing. The...
Avoiding out of gas for Truffle tests
How you do not have to worry about gas in tests anymore
You have probably seen this error message a lot of times: Error: VM Exception while processing transaction: out of gas Disclaimer : Unfortunately, this does not always actually mean what it is saying when using Truffle , especially for older versions. It can occur for various reasons and might be...
Design Pattern Solidity: Stages
How you can design stages in your contract
Closely related to the concept of finite-state machines, this pattern will help you restrict functions in your contract. You will find a lot of situations where it might be useful. Any time a contract should allow function calls only in certain stages. Let's look at an example: contract Pool {...
Web3 1.2.5: Revert reason strings
How to use the new feature
A new Web3 version was just released and it comes with a new feature that should make your life easier. With the latest version 1.2.5, you can now see the the revert reason if you use the new handleRevert option. You can activate it easily by using web3.eth.handleRevert = true . Now when you use...
Gaining back control of the internet
How Ocelot is decentralizing cloud computing
I recently came across an ambitious company that will completely redefine the way we are using the internet. Or rather, the way we are using its underlying infrastructure which ultimately is the internet. While looking at their offering, I also learned how to get anonymous cloud machines, you...
Devcon 5 - Review
Impressions from the conference
I had a lot to catch up on after Devcon. Also things didn't go quite as planned, so please excuse my delayed review! This year's Devcon was certainly stormy with a big typhoon warning already on day 1. Luckily (for us, not the people in Tokyo), it went right past Osaka. Nevertheless, a lot of...
Devcon 5 - Information, Events, Links, Telegram
What you need to know
Devcon 5 is coming up soon and there are already lots of events available, information about Osaka and more. Here is a short overview: Events Events Calendar Events Google Docs Events Kickback Most events are in all three, but if you really want to see all, you will have to look at all three...
Design Pattern Solidity: Off-chain beats on-chain
Why you should do as much as possible off-chain
As you might have realized, Ethereum transactions are anything but cheap. In particular, if you are computing complex things or storing a lot of data. That means sometimes we cannot put all logic inside Solidity. Instead, we can utilize off-chain computations to help us. A very simple example...
Design Pattern Solidity: Initialize Contract after Deployment
How to use the Initializable pattern
There are a few reasons why you might want to initialize a contract after deployment and not directly by passing constructor arguments. But first let's look at an example: contract MyCrowdsale { uint256 rate; function initialize(uint256 _rate) public { rate = _rate; } } What's the advantage over...
Consensys Blockchain Jobs Report
What the current blockchain job market looks like
Consensys published their blockchain jobs report which you can checkout in their Blockchain Developer Job Kit. The most interesting aspects are Blockchain developer jobs have been growing at a rate of 33x of the previous year according to LinkedIns jobs report Typical salary is about...
Provable — Randomness Oracle
How the Oraclize random number generator works
One particularly interesting approach by Provable is the usage of a hardware security device, namely the Ledger Nano S. It uses a trusted execution environment to generate random numbers and provides a Provable Connector Contract as interface. How to use the Provable Randomness Oracle? Use the...
Solidity Design Patterns: Multiply before Dividing
Why the correct order matters!
There has been a lot of progress since the beginning of Ethereum about best practices in Solidity. Unfortunately, I have the feeling that most of the knowledge is within the circle of experienced people and there aren’t that many online resources about it. That is why I would like to start this...
Devcon 5 Applications closing in one week
Devcon 5 Applications closing
Watch out for the Devcon 5 applications. You only have one week left to apply either as Buidler Student Scholarship Press Devcon is by far the biggest and most impressive Ethereum conference in the world. And it's full of developers! I am especially excited about the cool location this year in...
Randomness and the Blockchain
How to achieve secure randomness for Solidity smart contracts?
When we talk about randomness and blockchain, these are really two problems: 1. How to generate randomness in smart contracts? 2. How to produce randomness for proof-of-stake (POS) systems? Or more generally, how to produce trusted randomness in public distributed systems? There is some overlap...