Architecture

Ethereum Accounts

• nonce – a counter that increments with every transaction sent from the account. This ensures transactions are only processed once. For contract accounts, it the number of contracts created by the account.

• balance – amount of wei owned by the address

• codeHash – the hash of the code of an account on the EVM. Contract accounts contain code fragments that can perform different operations. This code gets executed if the account receives a message call. It cannot be changed, unlike the other account fields. For EOAs, the codeHash field is the hash of an empty string.

• storageRoot – keccak256 hash of the root node of a Merkle Patricia trie that encodes the storage contents of the account. empty by default.

Block Header

The block header of each block contains information on an Ethereum block.

The block header contains the following fields:

• Prev Hash - Keccak hash of the parent block

• Nonce - Used in proof of work computation

• Timestamp - Scale value of the output of UNIX time( )

• Uncles Hash - Keccak hash for uncled blocks

• Beneficiary - Beneficiary address, mining fee recipient

• LogsBloom - Bloom filter of two fields, log address & log topic in the receipts

• Difficulty - Scalar value of the difficulty of the previous block

• Extra Data - 32 byte data relevant to this block

• Block Num - Scalar value of the number of ancestor blocks

• Gas Limit - Scalar value of the current limit of gas usage per block

• Gas Used - Scalar value of the total gas spent on transactions in this block

• Mix Hash - 256-bit value used with a nonce to prove proof of work computation

• State Root - Keccak Hash of the root node of state trie (post-execution)

• Transaction Root - Keccak Hash of the root node of transaction trie

• Receipt Root - Keccak Hash of the root node of receipt trie

State Root

The state root is the root of the Merkle Patricia Trie which stores a key-value pair for every Ethereum account on the network, where the key is an Ethereum address and the value is the Ethereum account object.

Accounts

The Ethereum account is the consensus representation for an Ethereum address. It is made up of 4 items.

• Nonce - Number of transactions made by the account

• Balance - Balance of the account in Wei

• Code Hash - Hash of the bytecode stored in the contract/account

• Storage Root - Keccak Hash of the root node of storage trie (post-execution)

type StateAccount struct {
	Nonce    uint64
	Balance  *big.Int
	Root     common.Hash // merkle root of the storage trie
	CodeHash []byte
}

Storage Root

The storage root is the root of a Merkle Patricia Trie, where the keys are the storage slots and the values are the data in each slot.

Any change in contract storage will impact the Storage Root, which in turn will impact the State Root which in turn will impact the Block Header.