hederas-evm-equivalence-goals-and-exceptions.md

Understanding Hedera for EVM Developers

Hedera vs Ethereum

While Hedera strives for EVM equivalence, it's important to recognize certain unique aspects and fundamental differences in its network architecture and operations, such as the handling of state data structures, hashing algorithms, and the management of accounts and transactions. These distinctions in network behaviors are intentional design choices made to align with EVM standards, thereby achieving EVM compatibility. This approach ensures that while Hedera aligns closely with Ethereum, it also maintains its distinctive features and optimization.

Network and Security Differences

Function	Hedera	Ethereum
Network State Data Structure	Virtual Merkle Tree	Merkle Patricia Trie
Hashing Algorithm	SHA-384	Keccak-256*
Security	High security with aBFT	Secure with decentralized PoS network

{% hint style="info" %} *Note: Hedera'a EVM supports Keccak-256. Transactions received through EthereumTransaction (via the JSON-RPC relay) are hashed using Keccak-256. Only transactions using ED25519 keys through the Hedera API (HAPI) are hashed using SHA-384. {% endhint %}

Account and Authorization Differences

Function	Hedera	Ethereum
Authorization Signatures	Used for transaction authorization outside of smart contracts	Typically used within smart contracts
Special System Accounts	Available with unique properties	Not available
Non-ECDSA Accounts	Non-ECDSA accounts (such as ED or multi-key) are supported by Hedera and ECDSA accounts are fully compatible	ECDSA accounts are supported by Ethereum and non-ECDSA accounts are not supported/compatible
Account Deletion	Possible	Not possible

Contract and Gas Differences

Function	Hedera	Ethereum
Data Return on Static Calls	Data retrieval must be done through the relay	Data returned directly
Gas Fees	Charges at least 80% of gas fees regardless of transaction outcome	Gas fees depend on transaction outcome but typically 100% of the gas fees are charged and the unused portion is credited back
Contract Lifecycle	Contract entities can expire, rent fees may apply	No expiration or rent fees

Transactions and Queries Differences

Function	Hedera	Ethereum
Transaction Size Limit	6kb	No limit
Transaction Throttling	Transactions may be throttled by gas limits	Transactions pending until future submission
Query Costs	Not free, can use mirror node for free queries	Free read-only calls
Mempools	No mempools	Mempools available
Cost	Low, predictable fees (fraction of a cent)	Variable, often high gas fees

RPC Endpoint and Communication Differences

Function	Hedera	Ethereum
RPC Block Requests (e.g., eth_getBlockByHash* & eth_getBlockByNumber )	Return zero 32bytes hexadecimal value for the stateRoot	Returns the stateRoot hexadecimal value of the final state trie of the block
Communication	Requires communication with both consensus and mirror nodes	Direct communication with nodes

{% hint style="info" %} Note: Hedera Consensus and mirror nodes do not provide Ethereum RPC API endpoints. {% endhint %}

Token and Fee Differences

Function	Hedera	Ethereum
Native Tokens	Supports native tokens in addition to ERC-20 and ERC-721 token standards	All ERC token standards but primarily ERC-20 and ERC-721 tokens.
Fee Structure	Complex with two different gas prices	Single gas price
Token Association**	Concept of token association	No concept of token association
Keys for Token Functionality	Keys control access to token functionality (KYC, FREEZE, WIPE, supply, fee, and PAUSE)	No equivalent native functionality

{% hint style="info" %} **Note: Token Association only applies to native HTS tokens and does not affect ERC-20/721 tokens. {% endhint %}

Other Differences

Function	Hedera	Ethereum
Precheck Failures	Multiple precheck failure reasons	Typically single failure reason
HBAR Decimal Precision	8 or 18 (varies across Hedera APIs)	Consistent 18 point decimal precision