Explaining the Genesis Block ter Ethereum – Brandon Arvanaghi

Every blockchain has to begin somewhere, so there’s what’s called a genesis block at the beginning. This is the very first block, and te it the creators of Ethereum were at liberty to say “To commence, the following accounts all have X units of my cryptocurrency.” Any transfer of that ether on the blockchain will have originated from one of thesis initial accounts (or from mining).

Every time wij launch Ethereum, wij actually recreate this genesis block from scrape. Syncing the blockchain with peers only commences at block 1.

The genesis block is created using the genesis state opstopping or genesis.json te Geth. This verkeersopstopping contains all the gegevens that will be needed to generate block 0, including who starts out with how much ether. Here’s an example of a custom-built genesis state verkeersopstopping that initializes this block.

Let’s pauze down some of the fields te the genesis state opstopping. If you find this postbode useful, I encourage you to go after my Twitter account, where I postbode more tutorials and low-level explanations.


The config struct ter genesis.json has to do with setting configuration variables for Ethereum, and has nothing to do with what’s inwards block 0. However, thesis values are significant, because they also need to match the configuration information of any other knot you want to interact with.

There are three resources wij will look at when examining config .

  • The struct itself te Ethereum’s Go implementation.
  • How config is actually initialized when using Ethereum on the mainnet.
  • Where the variables are defined from the mainnet initialization.

Below is the config struct from the very first verbinding above.

config: chainID

This exists to tell the world which chain you are on. The mainnet chainID is 1, and it’s a quick way to tell other Ethereum clients “I want to participate on the mainnet chain” rather than “I will be creating my own chain that nobody else should care about.”

chainID wasgoed introduced te EIP155 (I will discuss what EIP is shortly). The intention ter adding it wasgoed to make transactions on the Ethereum network look different from those on the Ethereum classic network. Transactions are signed differently depending on the chainID used.

From the 2nd verbinding above, MainnetChainConfig sets ChainId to a MainNetChainID variable:

That MainNetChainID variable is defined te the utils.go verkeersopstopping spil 1.

For more information on signing discrepancies and a list of well-known chanIDs , go here.

config: HomesteadBlock

HomesteadBlock , when set to 0, means you will be using the Homestead release of Ethereum. This is expected, and the mainnet gensis configuration also has this set to 0.

config: DAOForkBlock

The block number where the Decentralized Autonomous Organization (DAO) fork takes place.

Some background: Te 2016, the DAO created a insanely successful wise contract for funding dApps and providing contributors a sort of equity stake te those dApps through DAO tokens. This contract wasgoed a novel idea that raised unprecedented amounts of ether.

Unfortuneately, an attacker discovered an attack vector that permitted ether to be withdrawn from the contract numerous times te exchange for the same DAO tokens. Millions were stolen.

Ultimately, a majority of Ethereum users voted to create a hard fork te the blockchain that would invalidate what the attackers did, and the contract would be updated. This wasgoed a controversial decision, spil the anti-fork faction (rightfully) claimed it set a dangerous precedent for the future: if the majority of users don’t like any particular outcome, there wasgoed now a precedent for undoing it.

Since the majority voted to proceed with this fork, the DAOForkBlock variable wasgoed born, and it occured on the 1920000th block te the mainnet. Here is the variable’s definition te Geth:

Thus, any block mined after this one would have to go after the protocols established by this fresh fork, and would be rejected otherwise. If wij were creating a local Ethereum chain to test on, wij might set this value to 0 so that wij get the most up-to-date transaction behavior from the get-go rather than use an outdated protocol for the very first 1919999 blocks.

config: DAOForkBlockSupport

A boolean value that confirms whether the knot abides by the DAO hard fork.

config: EIP150Block

EIP stands for Ethereum Improvement Proposal. Ethereum is open-source, so people make proposals te the form of discussions and code. Some are accepted, others rejected. EIP150 is one such proposal that wasgoed accepted.

This EIP took effect on block 2463000, and had mostly to do with enlargening gas prices ter response to denial-of-service concerns. Te the mainnet implementation of config , wij see:

config: EIP150Hash

The hash of the EIP150Block, which is needed for prompt sync.

config: EIP155Block

EIP155 wasgoed accepted to help prevent replay attacks.

config: EIP158Block

EIP158 wasgoed accepted to switch how Ethereum clients overeenkomst with empty accounts. This fresh protocol began treating them spil nonexistent, saving space on the blockchain.

config: Ethash

The Proof of Work mining protocol for mainnet. Ter mainnet, this config variable is initialized like so:

This simply tells the client we’re using Ethash, Ethereum’s Proof of Work algorithm, for mining blocks.

Now that we’re done looking at the config variable, wij can examine the surplus of the genesis.json verkeersopstopping.


This is the field that determines who starts out with how many ether to commence the blockchain. Te the Ethereum mainnet, this consisted of all the fortunate ducklings that participated te the Ethereum presale. Every time wij fire up Ethereum on the mainnet, wij recreate this very first block and all those initial transactions to those individuals.

Here are some of the addresses te the alloc section of the mainnet genesis state opstopping:


This value determines how hard it is to mine a block. Different blockchain technologies use different mining algorithms – Ethereum’s mainnet still uses Proof of Work spil of this writing. difficulty can be interpreted by its reciprocal, ter other words, when set to 0x4000 , it means there is a 1/1024 chance your very first attempt at mining a block succeeds.

Wij get this value because 0x4000 te hexadecimal is omschrijving to 1024 ter decimal. The reciprocal of 1024 is obviously 1/1024, which suggests on average you can expect a successful mining operation after 1024 hash computations. How swift you can mine that block depends on how rapid your pc can produce on average 1024 hash computations.

Think of this value spil the “seed” value for determining the difficulty to mine any block on the chain. Not every block will have this difficulty, instead, this value gets fed elsewhere ter the Ethereum client to algorithmically determine the difficulty for a subsequent block. The difficulty of mining a block switches spil the blockchain grows.

mixhash, nonce

mixhash and nonce are used together to determine if the block wasgoed mined decently. The reason wij have both is that if an attacker forges blocks with a false nonce , it can still be computationally costly for other knots ter the network to detect that the nonce wasgoed falsified. mixhash is an intermediary calculation to finding the nonce that is not spil costly to determine. Thus, if other knots on the network detect an errant mixhash when validating a block, they can discard the block without doing extra work to checking the nonce .

Thesis are meaningless te the genesis block, but making them random values is a good idea so that other peers don’t accidentally connect to your chain by having the same precies genesis.json opstopping.


The Keccak 256-bit hash of the previous block’s header. This is meaningless te the genesis block, since block 0 has no parent. However, the objective ter creating the genesis block wasgoed to make it have the same format spil any other block, so wij have this field and assign it a value.


The maximum number of computations any block on that chain can support.


The ether prizes gained from “mining” the genesis block go to the 160-bit coinbase address. This is meaningless te the genesis block (especially since you’re at liberty to allocate spil much ether spil you want to any account), but again, the objective wasgoed to make the genesis block look identical to any other block on the blockchain, so this values exist.


The output of the Unix time() function when the block wasgoed created.


For more Ethereum content, breakdowns, and blockchain-security posts go after @arvanaghi on Twitter.

Related movie: Emerald Coin: Mining an alternate crypto currency with your graphics card (Litecoin clone)

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