Ethereum blockchain

Ethereum blockchain

TL;DR: A replicated state machine: accounts hold balance + code + storage, the EVM mutates them deterministically per transaction, miners/proposers order blocks and you pay in gas. This is the mental model you need to read traces and reason about smart-contract bugs.

What it is

Ethereum is a quasi-Turing-complete distributed virtual machine. State is a Merkle-Patricia trie keyed by 20-byte addresses; each account is either an EOA (externally owned, controlled by a secp256k1 keypair) or a contract (code + per-account storage trie). A transaction is a signed message that triggers EVM execution, charging gas for every opcode. Since The Merge (Sep 2022) consensus is proof-of-stake; the post-Dencun (Mar 2024) data layer adds blob-carrying transactions (EIP-4844) used by rollups.

Preconditions / where it applies

  • Reading on-chain state, decoding tx traces, or writing PoCs that interact with mainnet/forknet
  • Understanding why a transaction reverted, who can call a function, what storage slot holds what
  • Building or auditing anything that runs on an EVM chain (Ethereum, Arbitrum, Optimism, Base, Polygon, BSC, Avalanche C-chain)

Technique

Key primitives to internalise:

  1. Accounts. EOA = address derived from keccak256(pubkey)[12:]. Contract = address derived from keccak256(rlp(sender, nonce))[12:] for CREATE or keccak256(0xff || sender || salt || keccak256(initcode))[12:] for CREATE2.
  2. Gas. Every opcode has a cost; tx specifies maxFeePerGas / maxPriorityFeePerGas (EIP-1559). The base fee is burned, priority fee paid to the proposer. Out-of-gas = revert.
  3. Storage. Per-contract slot map. mapping(k => v) lives at keccak256(abi.encode(k, slot)). Use cast storage <addr> <slot> to read.
  4. Calls. CALL runs target code in target context. DELEGATECALL runs target code in caller’s context (used by proxies — and the source of many ownership bugs). STATICCALL forbids state writes.
  5. Logs / events. Indexed topics + data, written to bloom filters in the block. The canonical attribution source.
  6. Reading state: 
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    cast call 0xCONTRACT "balanceOf(address)(uint256)" 0xVICTIM --rpc-url $RPC
cast storage 0xCONTRACT 0
cast 4byte-decode 0xa9059cbb000...
  7. Forking for PoC. anvil --fork-url $RPC --fork-block-number N gives you a local mainnet clone where you can vm.prank any address.

Detection and defence

  • Defenders use trace-level monitoring (Tenderly, Phalcon, OpenZeppelin Defender) to flag suspicious selfdestruct, delegatecall, large transfers.
  • For RPC providers: rate-limit eth_call with high gas, watch for debug_traceCall abuse.
  • For users: hardware wallets, EIP-712 typed-data signing prompts, and address book / simulation in the wallet UI.

Related: smart-contracts-overview, solidity-basics, foundry-toolkit.

References