account-service

Hiero Account Service (HAS) System Contract Functions

The Hiero Account Service (HAS) System Contract is accessible at address 0x16a on the Hiero network. This contract interface introduces a new account proxy contract to interact with other contracts for functionality such as HBAR allowances. It enables querying and granting HBAR approval to a spender account from within smart contracts, allowing developers to grant, retrieve, and manage HBAR allowances directly in their code. HAS also resolves between Hiero account-num aliases and EVM address aliases (HIP 632), and can verify whether a given address (Hiero account or EVM address) is authorized for a message and signature through the isAuthorized and isAuthorizedRaw methods.

The HAS interface is defined by IHederaAccountService.sol, with HIP-specific extension interfaces IHRC632.sol (alias resolution and signature verification) and IHRC906.sol (HBAR allowances). The abstract HederaAccountService.sol contract provides ready-to-use wrappers around each call.

The table below outlines the available Hiero Account Service System Contract functions:

Function Name	Function Selector Hash	Consensus Node Release Version	HIP	Method Interface
hbarAllowance	0xfec46666	0.52	HIP 906	hbarAllowance(address owner, address spender) external returns (int64 responseCode, int256 amount)
hbarApprove	0xa0918464	0.52	HIP 906	hbarApprove(address owner, address spender, int256 amount) external returns (int64 responseCode)
getEvmAddressAlias	0xdea3d081	0.54	HIP 632	getEvmAddressAlias(address accountNumAlias) external returns (int64 responseCode, address evmAddressAlias)
getHederaAccountNumAlias	0xbbf12d2e	0.54	HIP 632	getHederaAccountNumAlias(address evmAddressAlias) external returns (int64 responseCode, address accountNumAlias)
isValidAlias	0x308ef301	0.54	HIP 632	isValidAlias(address addr) external returns (int64 responseCode, bool response)
isAuthorizedRaw	0xb2a31da4	0.52	HIP 632	isAuthorizedRaw(address account, bytes memory messageHash, bytes memory signature) external returns (int64 responseCode, bool authorized)
isAuthorized	0xb2526367	0.56	HIP 632	isAuthorized(address account, bytes memory message, bytes memory signature) external returns (int64 responseCode, bool authorized)

The Hiero network also makes facade contract calls available to EOAs for an improved experience. Facade functions allow EOAs to make calls without requiring a deployed contract — the EOA calls its own account address directly. The table below outlines the available Hiero Account Service (HAS) System Contract facade functions:

Function Name	Function Selector Hash	Consensus Node Release Version	HIP	Method Interface	Defining Interface
hbarAllowance	0xbbee989e	0.52	HIP 906	hbarAllowance(address spender) external returns (int64 responseCode, int256 amount)	IHRC906AccountFacade.sol
hbarApprove	0x86aff07c	0.52	HIP 906	hbarApprove(address spender, int256 amount) external returns (int64 responseCode)	IHRC906AccountFacade.sol
setUnlimitedAutomaticAssociations	0xf5677e99	0.56	HIP 904	setUnlimitedAutomaticAssociations(bool enableAutoAssociations) external returns (int64 responseCode)	IHRC904AccountFacade.sol

Function Notes

• hbarAllowance — Returns the amount of HBAR the spender has been authorized to spend on behalf of the owner.
• hbarApprove — Authorizes spender to withdraw HBAR from the owner account up to amount. Calling it again overwrites the current allowance.
• getEvmAddressAlias — Returns the EVM address alias for a given Hiero account-num alias.
• getHederaAccountNumAlias — Returns the Hiero account-num alias for a given EVM address alias.
• isValidAlias — Returns true if the address is a Hiero account-num alias or an EVM address alias.
• isAuthorizedRaw — Verifies a signature for a message hash against an account. The signature must be a single ECDSA or ED25519 key, providing logic similar to ECRECOVER.
• isAuthorized — Verifies a signature for a message against an account, supporting possibly complex (multi-key) account key structures via a protobuf-encoded signature blob.
• setUnlimitedAutomaticAssociations — Enables or disables unlimited automatic token associations for the calling account.

All functions return an int64 responseCode (SUCCESS is 22) from HederaResponseCodes.sol.