Solidity Deep Dive: New Opcode 'Prevrandao'
All you need to know about the latest opcode addition
Let’s back up for a second and figure out what has changed since ‘The Merge’. The upgrade finally brought a new consensus mechanism to Ethereum. Instead of the old Proof of Work, blocks are now produced via Proof of Stake.
Proof of Work finds consensus via block hashes and a process called mining. In Ethereum prior The Merge miners typically would look for specific block-hashes using GPUs. This process was unpredictable and only solvable using brute-force. Hence if you find a fitting hash, you proved some work.
Now you prove some stake instead of work. A miner now is called a validator and each one has to put up 32 ETH as stake. New blocks are proposed by a validator that has the ‘correct’ 32 ETH stake.
Why Randomness in Proof of Stake?
But why does Ethereum even require randomness for its Proof of Stake protocol? Naively you might just design it, so that in a round-robin fashion, each validator will be chosen one after another in a pre-defined order.
But such a predictable fashion comes with a range of potential attacks.
- Denial of Service (DOS): If you know in advance who will be the next block proposers, you can more easily launch DOS attacks one by one for the chosen validators. If the order is random, you have less time to plan your attack.
- Selfish Validator Registrations: One could try to register especially advantageous validators that are chosen sooner and game the mechanism to earn more rewards.
- Bribing: You could also try to bribe validators in advance for blocks that might interest you to e.g. censor some specific transactions or not propose a block at all.
- Double-spending: Maybe one of the most critical attacks could be a double-spending attack. If you can predict the order in advance, it makes it easier to plan such an attack through a combination of bribing and simply owning a sequence of validators yourself. And you’ll know exactly which block you’ll be able to try your double-spend attack.
Enter the Randao
So how is the randomness in Ethereum created? In simple terms you have every validator in a given epoch pre-commit to a random number computed just locally. The final random number is every validator’s local random number combined via XOR (explicit or). The combination with XOR ensures that even just one single honestly computed random number of one of the validators in an epoch will lead to a new unmanipulated random number.
An epoch consists of 32 slots, so 32 potential validators and assuming all validators are online and proposing a new block, also a total of 32 blocks.
Technically validators are not even computing a local random number anymore actually. Instead they sign the current epoch number with their private key using BLS signatures. The signature is then hashed and used as random number. This simplifies the protocol while also allowing for multi-party validators, something that wouldn’t be possible with a commitment scheme.
Updating Randao
Once an epoch is finished, the newly computed randomness will be used to determine the validators in the next epoch. Technically actually the second next to give validators time to be learn and prepare themselves of their new roles, but that's a detail we can ignore.
And each shuffle is basically:
- Sign over current epoch number.
- Compute hash of signature.
- Calculate new randomness as Hash XOR Previous Randomness
Updating the Randao randomness like this has a few great properties.
- The hash ensures an even distribution over all possible random values => fairness to all possible outcomes.
- XOR makes sure that every single bit is affected, meaning that just one truly random value in one epoch will make the final result truly random.
- Signing over the epoch number (instead of e.g. the slot number) slightly decreases influence on future Randao epochs. Why?
- Imagine I have the last validator in one epoch. I can choose to reveal my signature which updates the Randao or not reveal the signature which would keep the previous Randao value. In total two possible outcomes, let's call them outcome A and B.
- Outcome A would give me the next epoch that ends with validators my own validator V1 followed by my own validator V0.
- Outcome B would give me the next epoch that ends with validators my own validator V0 followed by my own validator V1.
- The resulting influence on the randomness is the same for outcome A and B, so regardless of my choice, I will have the same influence.
- Imagine I have the last validator in one epoch. I can choose to reveal my signature which updates the Randao or not reveal the signature which would keep the previous Randao value. In total two possible outcomes, let's call them outcome A and B.
Biasability
We've touched on biasability a little bit already. Essentially it comes down to the last revealer problem.
- You cannot directly change the randomness.
- But you can choose to not sign the data in your slot.
And if you don't sign the data in your slot? Well no one else has the private key, so there is no way to get this data. And in this case the Randao update for the slot is simply skipped.
What is the cost of such an attack?
The block reward is roughly 0.044 ETH (depending on ETH inflation rates). Not signing simply means loosing this reward.
ultrasound.money has a nice visualization of staking inflation compared to transaction fees. The transaction fees since EIP-1559 are burnt, so if transaction fees in one block > block reward, ETH is actually deflationary.
Now if this happened to be the last slot in an epoch, then the final random value will be the one from the second last slot. And of course an attacker could even have control of multiple validators in the last slots of an epoch. So if an attacker controls the last four validators of an epoch, in each of the 4 slots he can choose to sign or not. In total giving him 2^4 = 16 possible total randomness values to choose from.
In other words for every controlled validator at the end of a slot, an attacker has a one bit influence on the final output.
Improving Biasability through VDFs
So we can see that the Randao randomness is biasable to some degree. The good news is that this doesn't break the Ethereum protocol security. So it's good enough for the protocol itself.
But can we improve on it anyways? Especially because Dapp developers like us might want a more secure, less biasable random number.
An improvement for this last revealer problem that Ethereum was planning is based on Verifiable Delay Functions (VDFs). It relies on computing some function that no one should be able to do in a time that is orders of magnitude faster than everyone else. One approach would be to enforce sequential computations, e.g. by sequential squarings of a number. You can see the talk from Justin Drake about this here.
The output of the VDF would then be used for updating the Randao value. So even the last revealer would not know the VDF output in time before having to decide to sign or not to sign.
Some research has been done into this already under https://www.vdfalliance.org/. But it's going to take quite some time for this to actually be implemented. No plans are made for this any time soon.
EIP-4399: A new Prevrandao opcode
Now with the understanding of how Randao works, say hello to EIP-4399 and a new opcode called 'prevrandao'. It was added in the Paris network upgrade.
To make it backwards compatible, the old block.difficulty opcode which used to give you the current block's Proof of Work difficulty, is now also returning the prevrandao value. The difficulty opcode doesn't make sense anymore now with Proof of Stake and re-using it like this is a nice way to add backwards compatibility for old contracts.
So what exactly is returned by prevrandao? Well the name makes it quite clear. You will get the Randao value from the latest Randao update. That means it’s from the last slot where someone actually updating the Randao and produced a new block.
Why not the new Randao from the current block? Because during block execution the new Randao value is not yet known. So keep that in mind for security, it’s the previous round value which is known at the time of execution.
How to use current Prevrandao
So with all that said, how can you actually use it prevrandao in a secure way? There are many things to consider and in many cases you’re better off just not using it for now until better methods exist.
Update: Solidity 0.8.18 now supports block.prevrandao. For any earlier versions, you need to use block.difficulty.
First the obvious, randomness from the past is known and predictable. So what shall we do? We pick a future prevrandao value.
How far in the future? Well this is where it gets tricky. And also where there is further support required in the EVM. EIP-4399 recommends to use:
- At least four epochs in the future. A new epoch ensures a new set of validators. And in particular four epochs ensures the network will miss at least one proposal further reducing Randao predicability.
- A slot that is not near the beginning of an epoch. Imagine you would use the validator in slot 4 of an epoch. It’s known roughly 6 minutes before the epoch runs who will be the validators in the new epoch. An attacker could use this time to try and bribe or attack these exact 4 validators. He can then gain knowledge of the randomness early, while also having an influence on the randomness, choosing between 2^4 = 16 different outcomes.
Unfortunately the EVM doesn't even currently allow to access the current epoch number. So all we could do is use the block number to approximate it. Remember a slot can be empty and not producing a block. That means if we wait 128 blocks we at least have the guarantee of waiting four full epoch, so let's do that.
There are now two ways you could implement it.
Idea 1: require future block >= n
We can enforce that a prevrandao value from a block higher or equal to the block of playing the game is used.
- In a first transaction you would determine the block number to be used.
- In a second transaction you would wait until the block number has passed and play the game.
This method of course allows validators to censor the second transaction and withhold it up to a moment where the prevrandao (block.difficulty) is a favorable value to them.
mapping (address => uint256) public gameWeiValues;
mapping (address => uint256) public blockNumbersToBeUsed;
function playGame() external payable {
uint256 blockNumberToBeUsed = blockNumbersToBeUsed[msg.sender];
if (blockNumberToBeUsed == 0) {
// first run, determine block number to be used
blockNumbersToBeUsed[msg.sender] = block.number + 128;
gameWeiValues[msg.sender] = msg.value;
return;
}
require(block.number >= blockNumbersToBeUsed[msg.sender], "Too early");
uint256 randomNumber = block.prevrandao; // block.difficulty
if (randomNumber != 0 || randomNumber % 2 == 0) {
uint256 winningAmount = gameWeiValues[msg.sender] * 2;
(bool success, ) = msg.sender.call{value: winningAmount}("");
require(success, "Transfer failed.");
}
blockNumbersToBeUsed[msg.sender] = 0;
gameWeiValues[msg.sender] = 0;
}mapping (address => uint256) public gameWeiValues;
mapping (address => uint256) public blockNumbersToBeUsed;
function playGame() external payable {
uint256 blockNumberToBeUsed = blockNumbersToBeUsed[msg.sender];
if (blockNumberToBeUsed == 0) {
// first run, determine block number to be used
blockNumbersToBeUsed[msg.sender] = block.number + 128;
gameWeiValues[msg.sender] = msg.value;
return;
}
require(block.number > blockNumbersToBeUsed[msg.sender], "Too early");
require(block.number < blockNumbersToBeUsed[msg.sender], "Too late");
uint256 randomNumber = block.prevrandao; // block.difficulty
if (randomNumber != 0 || randomNumber % 2 == 0) {
uint256 winningAmount = gameWeiValues[msg.sender] * 2;
(bool success, ) = msg.sender.call{value: winningAmount}("");
require(success, "Transfer failed.");
}
blockNumbersToBeUsed[msg.sender] = 0;
gameWeiValues[msg.sender] = 0;
}Idea 2: require future block == n
Alternatively we can enforce a specific block. Then we don’t have the issue of validators withholding the transaction.
- In a first transaction you would determine the block number to be used.
- In a second transaction you would wait until the exact block number and play the game.
This method of course has the issue that you may miss the block and would need to handle the case of not having any randomness.
WAY 1: require future block >= n
Pros:
- It allows playing the game at any time after block n.
Cons:
- It gives validators even more influence on randomness by censoring the playing the game transaction, so that it's included in a later block.
WAY 2: require future block == n
Pros:
- It doesn't give validators even more influence.
Cons:
- It allows playing the game only in block n. If you miss it, there's no way to get the value later.
How to use future Prevrandao(n)
Now if the prevrandao opcode could be used to obtain values in the past, that would be much better. This is a likely future feature.
So let's assume we had this feature. How could we change the game?
- We still determine the block of which we want to use the prevrandao value from.
- Then we simply wait for the block to arrive and retrieve it.
This time it doesn't matter if we miss it, because we can access the old prevrandao value.
You can follow the Ethereum Magicians Thread to be updated on any potential future EIPs.
// NOTE: below code is speculation on a possible future design
mapping (address => uint256) public gameWeiValues;
mapping (address => uint256) public blockNumbersToBeUsed;
function playGame() external payable {
uint256 blockNumberToBeUsed = blockNumbersToBeUsed[msg.sender];
if (blockNumberToBeUsed == 0) {
// first run, determine block number to be used
blockNumbersToBeUsed[msg.sender] = block.number + 128;
gameWeiValues[msg.sender] = msg.value;
return;
}
require(block.number >= blockNumberToBeUsed, "Too early");
uint256 randomNumber = block.prevrandao(blockNumberToBeUsed);
if (randomNumber != 0 || randomNumber % 2 == 0) {
uint256 winningAmount = gameWeiValues[msg.sender] * 2;
(bool success, ) = msg.sender.call{value: winningAmount}("");
require(success, "Transfer failed.");
}
blockNumbersToBeUsed[msg.sender] = 0;
gameWeiValues[msg.sender] = 0;
}
But keep in mind that still all things mentioned in the beginning about biasability still applies. A validator can still cause a re-shuffle.
The real long-term solution would be the addition of VDFs.
Solidity Developer
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Integrating the 0x API into your contracts
How to automatically get the best prices via 0x
How can you add 0x to your contracts to automatically convert between tokens? We have done this in a similar fashion before with Uniswap and Balancer. The 0x API has a bit of a twist. Let's take a look why... Why you want 0x in your contracts? It's simple: Okay, but seriously. Let's see why the...
How to build and use ERC-777 tokens
An intro to the new upgraded standard for ERC-20 tokens
The new upgraded standard for ERC-20 tokens is becoming more and more popular. It's fully backwards compatible, you can easily create one using the Openzeppelin contracts and there are many interesting new features not available in ERC-20. Should you upgrade from ERC-20? Well let's look into what...
COMP Governance Explained
How Compound's Decentralized Governance is working under the hood
You might have heard about the COMP token launch. With a current market cap of over 350 million USD, the token has accumulated massive value. But what is the actual utility of COMP? It's a governance token. Compound being a fully decentralized system (or at least on the way towards it), has a...
How to prevent stuck tokens in contracts
And other use cases for the popular EIP-165
Do you remember the beginning of the Dark Forest story? If not, let's look at it again: Somebody sent tokens to a smart contract that was not intended to receive tokens. This perfectly illustrates one of the issues not only with ERC-20 tokens, but generally with smart contracts. How can we find...
Understanding the World of Automated Smart Contract Analyzers
What are the best tools today and how can you use them?
As we all know, it's very difficult writing a complex, yet fully secure smart contract. Without the proper methods, chances are you will have many security issues. Automated security testing tools already exist and can be a great help. One of the main challenges for these tools is to maximize...
A Long Way To Go: On Gasless Tokens and ERC20-Permit
And how to avoid the two step approve + transferFrom with ERC20-Permit (EIP-2612)!
It's April 2019 in Sydney. Here I am looking for the Edcon Hackathon inside the massive Sydney university complex. It feels like a little city within a city. Of course, I am at the wrong end of the complex and I realize to get to the venue hosting the Hackathon I need to walk 30 minutes to the...
Smart Contract Testing with Waffle 3
What are the features of Waffle and how to use them.
Waffle has been a relatively recent new testing framework, but has gained a lot of popularity thanks to its simplicity and speed. Is it worth a try? Absolutely. I wouldn't run and immediately convert every project to it, but you might want to consider it for new ones. It's also actively being...
How to use xDai in your Dapp
Deploying and onboarding users to xDai to avoid the high gas costs
Gas costs are exploding again, ETH2.0 is still too far away and people are now looking at layer 2 solutions. Here's a good overview of existing layer 2 projects: https://github.com/Awesome-Layer-2/awesome-layer-2. Today we will take a closer look at xDai as a solution for your Dapp. What are...
Stack Too Deep
Three words of horror
You just have to add one tiny change in your contracts. You think this will take you only a few seconds. And you are right, adding the code took you less than a minute. All happy about your coding speed you enter the compile command. With such a small change, you are confident your code is...
Integrating the new Chainlink contracts
How to use the new price feeder oracles
By now you've probably heard of Chainlink. Maybe you are even participating the current hackathon? In any case adding their new contracts to retrieve price feed data is surprisingly simple. But how does it work? Oracles and decentralization If you're confused about oracles, you're not alone. The...
TheGraph: Fixing the Web3 data querying
Why we need TheGraph and how to use it
Previously we looked at the big picture of Solidity and the create-eth-app which already mentioned TheGraph before. This time we will take a closer look at TheGraph which essentially became part of the standard stack for developing Dapps in the last year. But let's first see how we would do...
Adding Typescript to Truffle and Buidler
How to use TypeChain to utilize the powers of Typescript in your project
Unlike compiled languages, you pretty much have no safeguards when running JavaScript code. You'll only notice errors during runtime and you won't get autocompletion during coding. With Typescript you can get proper typechecking as long as the used library exports its types. Most Ethereum...
Integrating Balancer in your contracts
What is Balancer and how to use it
What is Balancer? Balancer is very similar to Uniswap. If you're not familiar with Uniswap or Balancer yet, they are fully decentralized protocols for automated liquidity provision on Ethereum. An easier-to-understand description would be that they are decentralized exchanges (DEX) relying on...
Navigating the pitfalls of securely interacting with ERC20 tokens
Figuring out how to securely interact might be harder than you think
You would think calling a few functions on an ERC-20 token is the simplest thing to do, right? Unfortunately I have some bad news, it's not. There are several things to consider and some errors are still pretty common. Let's start with the easy ones. Let's take a very common token: ... Now to...
Why you should automatically generate interests from user funds
How to integrate Aave and similar systems in your contracts
If you're writing contracts that use, hold or manage user funds, you might want to consider using those funds for generating free extra income. What's the catch? That's right, it's basically free money and leaving funds unused in a contract is wasting a lot of potential. The way these...
How to use Polygon (Matic) in your Dapp
Deploying and onboarding users to Polygon to avoid the high gas costs
Gas costs are exploding again, ETH2.0 is still too far away and people are now looking at layer 2 solutions. Here's a good overview of existing layer 2 projects: https://github.com/Awesome-Layer-2/awesome-layer-2. Today we will take a closer look at Polygon (previously known as Matic) as a...
Migrating from Truffle to Buidler
And why you should probably keep both.
Why Buidler? Proper debugging is a pain with Truffle. Events are way too difficult to use as logging and they don't even work for reverted transactions (when you would need them most). Buidler gives you a console.log for your contracts which is a game changer. And you'll also get stack traces...
Contract factories and clones
How to deploy contracts within contracts as easily and gas-efficient as possible
The factory design pattern is a pretty common pattern used in programming. The idea is simple, instead of creating objects directly, you have an object (the factory) that creates objects for you. In the case of Solidity, an object is a smart contract and so a factory will deploy new contracts for...
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...
Downsizing contracts to fight the contract size limit
What can you do to prevent your contracts from getting too large?
Why is there a limit? On November 22, 2016 the Spurious Dragon hard-fork introduced EIP-170 which added a smart contract size limit of 24.576 kb. For you as a Solidity developer this means when you add more and more functionality to your contract, at some point you will reach the limit and when...
Using EXTCODEHASH to secure your systems
How to safely integrate anyone's smart contract
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?
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...