How to use IPFS in your Dapp?
Using the interplanetary file system in your frontend and contracts
You may have heard about IPFS before, the Interplanetary File System. The concept has existed for quite some time now, but with IPFS you'll get a more reliable data storage, thanks to their internal use of blockchain technology. Filecoin is a new system that is incentivizing storage for IPFS nodes.
If you are participating in the HackFS, a current hackathon sponsored by ETHGlobal and Protocol Labs (the makers of IPFS), or not, knowing IPFS will be a useful skill for your Dapp developments.
Can't you just store all data in the Ethereum blockchain directly?
Excellent question and in theory yes. But remember that data in the Ethereum blockchain is shared between every single node. This is extremely inefficient for large sets of data. So really the only solution is to have only some nodes storing the data. That's exactly what IPFS is doing. Files are randomly allocated to a subset of nodes.
How does it work?
The whole system is quite complex and even the 11-pages whitepaper doesn't cover everything in detail. The core principle is a DHT (distributed hash table). It's using Kademlia to distribute files to nodes. We won't go into details about this here, but read the great article that I linked. In short, you want files to be distributed somewhat randomly, but with short paths for every file between the nodes (to reduce latency), while being DOS-resistant. And that's what Kademlia is achieving.
IPFS builds several services on top. The upcoming Filecoin will introduce a way to pay IPFS nodes for storing files. Currently IPFS is still free to use, but also less reliable, see the next question. You'll further get an IPNS naming system, a unique hash per file, file permissions and Bittorrent-like features.
Is it secure and reliable?
In short no, but it depends what we mean with 'reliable'. You cannot store a file in IPFS, then try to read it two years later and still expect it to be there. Nodes will garbage collect unused files. But it's very reliable for frequently used files. And is it secure? Data is all public, so if you are concerned about privacy, you need to encrypt the files.
Adding IPFS to Solidity contracts
The Solidity part will be very simple. We will only store the IPFS hash of users inside our contract:
// SPDX-License-Identifier: MIT
pragma solidity ^0.6.11;
contract IpfsStorage {
mapping (address => string) public userFiles;
function setFile(string memory file) external {
userFiles[msg.sender] = file;
}
}Compile and deploy the contract, or if you're lazy use the one I deployed in the Kovan network: https://kovan.etherscan.io/address/0x8c700a5f78d61e350e7bd7d85a6e688bbbb8a7af.
Now let's go ahead and build the frontend. We will use the create-eth-app as starting point. Install it using yarn create eth-app my-eth-app. Next we can add IPFS to it:
yarn workspace @project/react-app add ipfsThe full Javascript IPFS documentation is available here. Be aware that it's still very much work in progress.
Okay, now let's initialize IPFS. It creates and connects an IPFS node that we can use to read and upload files.
import IPFS from "ipfs";
async function initIpfs() {
node = await IPFS.create();
const version = await node.version();
console.log("IPFS Node Version:", version.version);
}Now that we have the IPFS node, let's add a function to read the current file from the contract.
We use the ethers.js library with our current address.
async function readCurrentUserFile() {
const result = await ipfsContract.userFiles(
defaultProvider.getSigner().getAddress()
);
return result;
}Let's upload a file to IPFS and store it in our contract.
- uploadFile: This will be the function to take a file and upload it to IPFS using our IPFS node.
setFile: After a successful upload, we can store the IPFS hash inside our contract using this function.
async function setFile(hash) {
const ipfsWithSigner = ipfsContract.connect(defaultProvider.getSigner());
await ipfsWithSigner.setFile(hash);
setIpfsHash(hash);
}
async function uploadFile(file) {
const files = [{ path: file.name + file.path, content: file }];
for await (const result of node.add(files)) {
await setFile(result.cid.string);
}
}Now let's add a nice drag zone for the user to upload a file in the browser. And put it all together.
Please check out the live demo and repository for the full example.
- Repository: https://github.com/gorgos/IPFS-Dapp
- Live Demo: https://ipfs-dapp.netlify.app/
Some alternatives
- Swarm: Very similar to IPFS, you can use it the same way. It has a bigger focus on Ethereum relying on smart contract incentives. However, it's not quite as matured yet.
- SKALE Filestorage: Side chains are effectively using a subset of Ethereum nodes allowing for more data to be stored inside them. Skale made use of that and introduced their own file-storage sytem. SKALE was launched to mainet only a few weeks ago, so you can go ahead and try it.
Solidity Developer
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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?
Update 2023 : Ethereum transitioned to Proof of Stake! If you are interested in the randomness there, you can now use the updated info over at https://soliditydeveloper.com/prevrandao. When we talk about randomness and blockchain, these are really two problems: How to generate randomness in smart...