Wrapped HBAR (WHBAR)

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WHBAR (ERC) in the Hedera Ecosystem

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Core Functionalities

• Deposit & Mint: When you call the deposit() function and send HBAR, the contract mints an equivalent amount of WHBAR. Each unit of HBAR (represented in tinybars with 8 decimals) is matched with one unit of WHBAR. This ensures that the wrapped token maintains parity with the native token.
• Withdraw & Burn: To redeem your underlying HBAR, you call the withdraw(amount) function. The contract burns the specified WHBAR tokens and releases the corresponding HBAR back to your wallet. This burn mechanism is crucial for maintaining the correct token supply and preserving the peg between HBAR and WHBAR.
• ERC20 Standard Compliance: WHBAR implements all standard ERC20 functions (e.g., transfer, approve, transferFrom), ensuring seamless interaction with wallets, exchanges, and various DeFi protocols that support ERC20 tokens.

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Implementation Guide

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Wrapping HBAR

• Native HBAR: Uses 8 decimal places (tinybars).
• WHBAR (ERC20): Uses 8 decimal places (tinybars) throughout — balances, transfers, deposit(), and withdraw(). deposit() simply mints an amount of WHBAR equal to the msg.value it receives, and msg.value is tinybar during EVM execution. The 18-decimal weibar form is only the transaction value an off-chain caller submits; the relay converts it to tinybar before deposit() runs.

• From off-chain tooling (ethers/viem/wallet): set the transaction value in weibar (10¹⁸ per HBAR). The relay converts it to tinybar, so sending 10 * 10**18 weibar wraps 10 HBAR → 10 WHBAR.
• From another contract: the value is tinybar (no conversion) — use 10 * 10**8 for 10 HBAR. Passing 10 * 10**18 here would send 10¹⁸ tinybar, which exceeds the total HBAR supply and reverts.

/**
 * @notice Wrap 10 HBAR into WHBAR from within a contract.
 * @dev Contract-to-contract `value` is TINYBAR (8 decimals): 1 HBAR = 1e8.
 */
function wrapTenHbar() public {
    whbarContract.deposit{value: 10 * 10**8}(); // 10 HBAR
}

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Unwrapping WHBAR

/**
 * @notice Burns WHBAR tokens and returns the equivalent HBAR
 * @param amount The amount of WHBAR to burn
 */
function withdraw(uint256 amount) public {
    // To unwrap 5 WHBAR back to HBAR
    whbarContract.withdraw(5 * 10**8);
}

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Standard ERC20 Functions

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Contract Deployments

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Security Considerations:Audit and Testing

• Audit and Review:
  Although the WHBAR contract has been independently reviewed, developers and users should conduct their own security assessments. Even small oversights in smart contracts may lead to vulnerabilities.
• Test in a Sandbox:
  Always test interactions in a testnet environment before deploying or integrating with mainnet contracts. This helps ensure the behavior matches expectations.
• Follow Best Practices:
  Double-check function inputs and transaction amounts. Always use the designated functions (deposit() and withdraw()) to prevent unintended fund loss.

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Integration Best Practices

• Check allowances: Before attempting transferFrom operations, verify that sufficient allowance has been granted.
• Verify contract addresses: Always double-check you’re interacting with the official WHBAR contract addresses listed in the documentation.
• Handle decimals properly: Since both HBAR and WHBAR use 8 decimals, calculations are straightforward. Only for deposits, use 18 decimals to represent weibars.