Hedera

## Account Model (Critical Difference) - Hedera accounts must be created before receiving funds — unlike Bitcoin/Ethereum, addresses don't exist until created - Account creation costs HBAR — someone must fund the initial creation - Account IDs are numeric (0.0.12345) — not cryptographic hashes like other chains - Memo field available on accounts — can store small amounts of data - Accounts can be deleted to recover balance — but requires all tokens and associations removed first ## Account Creation - New users need someone to create their account — can't just generate address and receive - Exchanges create accounts on withdrawal — but self-custody requires creation first - HashPack and other wallets offer account creation — may require payment or sponsor - Testnet accounts free to create — use for development and testing ## Transaction Fees - Fees are extremely low and predictable — typically $0.0001 or less - Fees paid in HBAR only — no gas token complexity - Transaction fees set by network, not auction — no priority fee bidding - Scheduled transactions cost extra — pay for scheduling plus execution ## Token Service (HTS) - Native token support without smart contracts — create tokens via Hedera Token Service - Token association required before receiving — must explicitly associate with token ID - Association costs small HBAR fee — limits spam tokens - Fungible and NFT tokens supported natively — no need for custom contracts - Token admin keys control supply, freeze, wipe — verify token permissions before trusting ## Memo Field - Transactions can include memo — used for exchange deposits like destination tags - Memo is public and permanent — don't include sensitive data - Some services require specific memo format — verify before sending - Max memo size is 100 bytes — keep it short ## Consensus and Finality - Transactions finalize in 3-5 seconds — no waiting for confirmations - Hashgraph consensus provides ordering guarantees — no MEV or frontrunning possible - Fair ordering prevents manipulation — transactions processed in order received - Mirror nodes provide historical data — main network doesn't store full history ## Smart Contracts - Hedera supports Solidity smart contracts — EVM compatible - Contracts interact with native HTS tokens — best of both worlds - Contract deployment costs more than simple transactions — plan accordingly - State storage costs ongoing rent — unused contracts still cost ## Staking - Native staking to nodes — no minimum, no lockup - Rewards paid automatically every 24 hours — no claiming needed - Staking doesn't transfer funds — HBAR stays in your account - Choosing a node affects decentralization — spread stakes across nodes ## Keys and Security - Accounts can have multiple keys — threshold signatures supported - Key rotation possible without changing account ID — update keys if compromised - Different key types: Ed25519, ECDSA (secp256k1) — affects wallet compatibility - Admin keys on tokens can freeze/wipe holdings — check before acquiring tokens ## Common Issues - "INSUFFICIENT_PAYER_BALANCE" — need more HBAR for fees - "INVALID_ACCOUNT_ID" — account doesn't exist, needs creation - "TOKEN_NOT_ASSOCIATED" — must associate with token before receiving - "INSUFFICIENT_TX_FEE" — rare, fee estimate was too low - "ACCOUNT_FROZEN_FOR_TOKEN" — token admin has frozen transfers ## Exchanges and Transfers - Most major exchanges support HBAR — verify account ID format (0.0.xxxxx) - Memo often required for exchange deposits — critical like XRP destination tags - Account ID is not a wallet address — don't confuse with Ethereum-style addresses - Verify recipient account exists before sending — non-existent accounts reject transfers ## Network Services - Hedera Consensus Service (HCS) — ordered message logging - Hedera File Service (HFS) — store larger data on network - Mirror nodes for queries — don't query mainnet for historical data - SDKs available for major languages — JavaScript, Java, Go, Python