How Ethereum scales with Arbitrum Nitro and how to use it

A blockchain on a blockchain deep dive

Have you heard of Arbitrum Nitro? The new WAVM enables Plasma but for smart contracts in a super efficient way! It enables having a side chain with guarantees of the Ethereum mainnet chain. Arbitrum has already been one of the most successful Layer 2s so far, and the new Nitro is a major upgrade for it.

Let's start at the beginning...

What are Merkle Trees?

Merkle Trees are at the foundation of how this scaling technology works. At the root of the Merkle tree is the root hash. It's created by hashing all its original values as leaf nodes. Now two leaf hashes are combined by creating a new hash just for those together. We do this all the way until we have one tree with a single root hash. A Merkle proof now is a way for you to prove to someone who only knows the root hash that any value is in fact part of this tree as one of the leafs.

I wrote a long guide on Merkle Trees in case you want to dive deeper into the topic.

State of a smart contract

In Ethereum one Merkle tree is the state tree which contains all state like user ETH balances, but it also contains the contract storage itself. This allows us to create Merkle proofs on smart contract state!

So it's possible to prove a smart contract has a certain state using the Merkle proof mechanism. Keep that in mind for later.

How does Plasma work?

Plasma uses a combination of smart contracts and Merkle proofs. Together, these enable fast and cheap transactions by offloading these transactions from the main Ethereum blockchain into a plasma chain. In contrast to regular sidechains, you cannot run any smart contract in here.

In Plasma users send transactions between each other in UTXO style where the results of new balances are continuously updated in the Ethereum smart contract as Merkle tree roots. Once a Merkle root is updated in the smart contract, it gives users the security over their funds even if the plasma chain operator is malicious. The root encapsulates the result from many sent funds transactions. Should a Plasma operator submit an invalid root, users can contest it and safely get their funds back. For more details have a look here.

But as said before, it cannot run smart contracts. So no Uniswap with Plasma is possible.

Arbitrum: How to run a blockchain on a blockchain

But this is where Arbitrum comes in. It's Plasma for smart contracts!

Yo Dawg Optimism

The core idea here is actually quite simple. Just like in Plasma you have a layer 2 chain which is running all transactions and you update only the Merkle root within layer 1 occasionally. The Merkle root in this case is not for UTXO transactions as for regular plasma, but for the full state of a smart contract. Or rather for the full state of all smart contracts being used.

Yes this means we can run arbitrary smart contracts on Arbitrum! In very short, this is how it works:

  • Represent smart contract states as Merkle tree
  • Run all transactions only on the Arbitrum chain
  • Continuously update the state roots on Ethereum layer 1
  • Arbitrum chain has low security, but through the state roots on Ethereum, they enable fraud proofs
    • When a validator from layer 2 submits a malicious state root and it's contested, they loose their bond.
    • Fraud proofs are gas expensive, but more efficient than Optimism through an interactive mechamism (see details below).
    • Run single execution step which is contested with prover submitting any required state.

Now you might realize, this is where the scaling comes from. You only run transactions on layer 1 that are contested with a fraud proof. That’s the gain. So the scaling advantage comes solely from the fact that you won’t run 99.9% of transactions on layer 1.

Arbitrum Detailed Overview

The big ideas behind Arbitrum Nitro are:

  1. Sequencing 
  2. Geth at the core
  3. Wasm for Proving
  4. Optimistic Rollups via Interactive Fraud Proofs
Arbitrum Sequencing

To actually run the transactions, we need native Geth, Geth with Wasm and Merkle Proofs. The architecture looks like this:

  • On the highest level you have blockchain node functionality.
  • ArbOS handling L2 functionlity like batch decompression and bridging.
  • Core Geth EVM contract execution either native or via WASM.
Geth at core

How are transactions included?

New transactions can be added in three ways:

  1. Normal Inclusion by Sequencer
  2. Message from L1 included by Sequencer
  3. Message from L1 force-included on L2

1. Normal Inclusion by Sequencer

In the normal case the currently still centralized sequencer will add new messages to the inbox. This is done by calling addSequencerL2Batch. Here we check that the sender is the stored sequencer, only he is allowed to call this function:

function addSequencerL2Batch(
    uint256 sequenceNumber,
    bytes calldata data,
    uint256 afterDelayedMessagesRead,
    IGasRefunder gasRefunder,
    uint256 prevMessageCount,
    uint256 newMessageCount
) external override refundsGas(gasRefunder) {
    if (
        && msg.sender != address(rollup)
    ) revert NotBatchPoster();


And then inside addSequencerL2BatchImpl the bridge is called to enqueue the message to the inbox:


Which then calls enqueueSequencerMessage in the bridge which simply adds a new hash to the inbox array:

bytes32[] public sequencerInboxAccs;

function enqueueSequencerMessage(
    bytes32 dataHash,
    uint256 afterDelayedMessagesRead,
    uint256 prevMessageCount,
    uint256 newMessageCount
    returns (
        uint256 seqMessageIndex,
        bytes32 beforeAcc,
        bytes32 delayedAcc,
        bytes32 acc
    acc = keccak256(abi.encodePacked(beforeAcc, dataHash, delayedAcc));

2. Message from L1 by Sequencer

Messages can also be added by anyone directly using calls in L1. This is useful for example when making deposits from L1 to L2.

Eventually this will call enqueueDelayedMessage on the bridge inside deliverToBridge.

bytes32[] public delayedInboxAccs;

function enqueueDelayedMessage(
    uint8 kind,
    address sender,
    bytes32 messageDataHash
) external payable returns (uint256) {
function deliverToBridge(
    uint8 kind,
    address sender,
    bytes32 messageDataHash
) internal returns (uint256) {
       bridge.enqueueDelayedMessage{value: msg.value}(

3. Message from L1 force-included on L2

There is one issue with the second case. A sequencer can take messages from the delayed inbox and process them, but he may also simply ignore them. In that case messages might not ever end up in L2. And since the sequencer is still centralized, there is a third backup option called forceInclusion.

Anyone can call this function and should the sequencer stop posting messages for a minimum amount of time, it allows others to continue posting messages.

So why is there a delay at all and why not allow users always  immediately to force include transactions? If the sequencer has priority, he can give soft-confirmations about transactions to users, leading to a better UX. If there would be constant force inclusions, the sequencer cannot pre-confirm to users what will happen. Why? Well, a force-included transaction may invalidate one that the sequencer was planning to post.

function forceInclusion(
    uint256 _totalDelayedMessagesRead,
    uint8 kind,
    uint64[2] calldata l1BlockAndTime,
    uint256 baseFeeL1,
    address sender,
    bytes32 messageDataHash
) external {

    if (l1BlockAndTime[0] + maxTimeVariation.delayBlocks >= block.number)
        revert ForceIncludeBlockTooSoon();
    if (l1BlockAndTime[1] + maxTimeVariation.delaySeconds >= block.timestamp)
        revert ForceIncludeTimeTooSoon();



How do the Fraud Proofs work?

Let's explore how the frauf proofs of Arbitrum Nitro work in detail.


New in Arbitrum Nitro is the WAVM. They basically re-use the Geth Ethereum Node code and compile it to Wasm (or rather a slightly modified version of Wasm). Wasm stands for Web Assembly and is an environment which allows running code regardless of the platform. So similar to the EVM, but without gas. It’s also a web-wide standard, so it has more support by other languages and better performance. So compiling the Geth code written in Go into Wasm is indeed possible.

How does this Wasm execution help us?

Math Proof Meme

We can run proofs for it! Because it’s a controlled execution environment, we can replicate its execution inside a Solidity smart contract. That is the requirement for running fraud proofs.

So are we just running everything within the WAVM? Well Wasm is still slower execution compared to native compiled code. But here’s the beauty of Nitro: The same Geth code will be compiled to Wasm for the proving, but to native code for execution. This way we can get the best of both worlds: Run the chain with native performance, but still be able to execute proofs.

2. Fraud Proofs

Fraud Meme

Now let’s take a look how these fraud proofs work in detail. What do we need?

  1. We need a mechanism to get pre- and post-state of an execution.
  2. We need to be able to run the WAVM execution in a Solidity contract.
  3. We need an interactive mechanism to determine which execution step to prove.

The last step is optional, but a performance improvement if we only require a proof for one single execution. It does however require a few additional interactive steps between challenger and challenged node. We won’t go into the details for that, but you can read more about it here. And of course in the source code directly.

But we will go into detail about the other two parts now.

3. Get Pre- and Post-state of an Execution

During the interactive challenge, eventually the challenger will point down to a single execution disagreement. This single execution has a known pre- and post-execution state Merkle root hash. The post-execution hash is challenged, so in the end we will compare it to what we got from executing it ourselves. The pre-execution hash is not challenged and thus trusted.

It will be used to initialize the WAVM machine:

struct Machine {
    MachineStatus status;
    ValueStack valueStack;
    ValueStack internalStack;
    StackFrameWindow frameStack;
    bytes32 globalStateHash;
    uint32 moduleIdx;
    uint32 functionIdx;
    uint32 functionPc;
    bytes32 modulesRoot;

The challenger will initialize this machine with all the data.

In the contract we then only need to double check that this data represents the stored Merkle root hash:

require(mach.hash() == beforeHash, "MACHINE_BEFORE_HASH")

Now we can also trust the modules root and use it to verify the modules data.

A module is defined as:

struct Module {
    bytes32 globalsMerkleRoot;
    ModuleMemory moduleMemory;
    bytes32 tablesMerkleRoot;
    bytes32 functionsMerkleRoot;
    uint32 internalsOffset;

This holds data in the form of further Merkle root hashes for WAVM machine data. And the challenger also initializes this data.

The contract again just verifies it with the previous modulesRoot:

(mod, offset) = Deserialize.module(proof, offset);
(modProof, offset) = Deserialize.merkleProof(proof, offset);
    modProof.computeRootFromModule(mach.moduleIdx, mod) == mach.modulesRoot,

And lastly we do the same again for the instruction data:

struct Instruction {
    uint16 opcode;
    uint256 argumentData;

And it will be verified via the functionsMerkleRoot:

MerkleProof memory instProof;
MerkleProof memory funcProof;
(inst, offset) = Deserialize.instruction(proof, offset);
(instProof, offset) = Deserialize.merkleProof(proof, offset);
(funcProof, offset) = Deserialize.merkleProof(proof, offset);
bytes32 codeHash = instProof.computeRootFromInstruction(mach.functionPc, inst);
bytes32 recomputedRoot = funcProof.computeRootFromFunction(
require(recomputedRoot == mod.functionsMerkleRoot, "BAD_FUNCTIONS_ROOT");

So now we have an initialized WAVM machine and all that is left to do is execute this one single operation. This now depends on the exact instruction we need to run.

Take for example a simple addition. This is extremely simple:

uint32 b = mach.valueStack.pop().assumeI32();
uint32 a = mach.valueStack.pop().assumeI32();
return (a + b, false);

That’s basically it. Take the first two values from the machine stack and add them together.

Let’s look at another instruction. A local get instruction:

function executeLocalGet(
    Machine memory mach,
    Module memory,
    Instruction calldata inst,
    bytes calldata proof
) internal pure {
    StackFrame memory frame = mach.frameStack.peek();
    Value memory val = merkleProveGetValue(frame.localsMerkleRoot, inst.argumentData, proof);

The StackFrame comes from the WAVM initialization where we can find the localsMerkleRoot:

struct StackFrame {
    Value returnPc;
    bytes32 localsMerkleRoot;
    uint32 callerModule;
    uint32 callerModuleInternals;

And via Merkle Proof we can retrieve the value and push it to the stack.

Lastly we double check that the resulting final hash from this computational step equals the stored hash:

    afterHash != selection.oldSegments[selection.challengePosition + 1],

Only if it doesn't match, the proof is valid and we continue. Now the challenger has won and a new post-state will be accepted.

How to implement on Arbitrum yourself

Arbitrum fully supports Solidity, so you can take your contracts as they are with just a few caveats:

  • blockhash(x) returns a cryptographically insecure, pseudo-random hash.l return 0.
  • block.coinbase returns zero
  • block.difficulty returns the constant 2500000000000000
  • block.number / block.timestamp return an "estimate" of the L1 block
  • msg.sender works the same way it does on Ethereum for normal L2-to-L2 transactions; for L1-to-L2 "retryable ticket" transactions, it will return the L2 address alias of the L1 contract that triggered the message. See retryable ticket address aliasing for more.

How to use the Arbitrum networks

Those are the two important Aribtrum networks. You can use the wallet_addEthereumChain functionality from supported wallets like MetaMask or otherwise users will manually need to add the network.

For now the mainnet is still operating on the older architecture. But the Rinkeby testnet is fully upgraded to the new Arbitrum Nitro stack.

To get funds use the bridge available at

const params = [{
  "chainId": "42161", // testnet: "421611"
  "chainName": "Arbitrum",
  "rpcUrls": [
    // rinkeby: ""
    // goerli: ""
  "nativeCurrency": {
    "name": "Ether",
    "symbol": "ETH",
    "decimals": 18
  "blockExplorerUrls": [
    // rinkeby: ""
    // goerli: ""

try {
    await ethereum.request({
        method: 'wallet_addEthereumChain',
} catch (error) {
    // something failed, e.g., user denied request
    arbitrum_mainnet: {
        provider: function () {
          return new HDWalletProvider(
                + infuraKey,
    arbitrum_rinkeby: {
        provider: function () {
          return new HDWalletProvider(
    arbitrum_goerli: {
        provider: function () {
          return new HDWalletProvider(

How to deploy to the Arbitrum networks

Now you can add the Arbitrum Mainnet into Truffle or Hardhat as shown left.

A good practice I would recommend is writing your tests with Hardhat with a regular config, so you can run the tests fast and with console.log/stacktraces. And only occasionally use Truffle to run tests against a testnet.

Lastly you will need to activate Arbitrum in the Infura settings:

Infura Optimism

Markus Waas

Solidity Developer

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    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 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...

  • Decentralized Etherscan

    Sourcify: 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...

  • 0x Contracts

    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...

  • 777

    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...

  • Compound Governance

    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...

  • Stuck Car

    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...

  • Automated Security Tools

    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...

  • Long Way

    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...

  • Waffles

    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...

  • xDai

    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: Today we will take a closer look at xDai as a solution for your Dapp. What are...

  • 15 Stacks

    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...

  • Chainlink Thumbnail

    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

    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...

  • truffle buidler typescript

    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...

  • Balance Rope

    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...

  • mousetrap

    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...

  • Aave

    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...

  • Matic Logo

    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: 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...

  • Factory

    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...

  • IPFS logo

    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...

  • tiny-kitten

    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...

  • Uniswap

    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...

  • Continuous Integration

    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...

  • Devcon 6

    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:...

  • ERC-2020

    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...

  • hiring

    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...

  • People making fun

    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...

  • React and Ethereum

    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...

  • Solidity Overview

    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...