Ether Wrapper: Minting sETH with Ether directly¶

The EtherWrapper, introduced with SIP-112, brings with it the ability to mint sETH directly using either ETH in the NativeEtherWrapper or WETH in the EtherWrapper itself.

Tip: Native Ether

As the EtherWrapper has been designed for both L1 and L2 Optimism, it supports WETH (wrapped ether) by default. Thus when using the NativeEtherWrapper contract on L1, the Ether is simply wrapped on it's way and as such to see the total amount of Ether in both wrappers, simply look at the WETH holdings of https://contracts.synthetix.io/EtherWrapper.

Using Wrapper Ether (all environments)¶

Destination contract (address & ABI): EtherWrapper

Views¶

burnFeeRate The percentage (stored as a decimal with 18 places) of sETH that will be deducted when burning
capacity The remaining amount of WETH that can be sent to the EtherWrapper
mintFeeRate The percentage (stored as a decimal with 18 places) of sETH that will be deducted when minting
getReserves The amount of WETH held in the EtherWrapper (this includes all Ether that was sent via the NativeEtherWrapper which wraps to WETH first)

Mint sETH with WETH¶

Methods¶

mint(uint amount)

WETH Approval Required to Mint

EtherWrapper needs to be approved to spend the user's WETH (as it needs to send it to itself for payment)

Events Emitted¶

For each mint, among other events, one primary event will be emitted:

name	emitted on	`address account`	`uint principal`	`uint fee`	`uint amountIn`
`Minted`	`EtherWrapper`	`msg.sender`	The `amount` minus the `fee` (or the remaining `capacity` of the EtherWrapper if `amount` would reach the limit.)	the fee in `sETH` that is deducted via the `mintFeeRate`	the total `amountIn`

Example Transactions on Mainnet¶

EtherWrapper.mint(6e18)

Burn sETH to WETH¶

Contract¶

Destination contract (address & ABI): EtherWrapper

Methods¶

burn(uint amount)

No Approval Required to Burn

EtherWrapper does NOT need approval to burn, as sETH can be burned in-place directly using protected functionality.

Events Emitted¶

For each burn, among other events, two will be emitted:

name	emitted on	`address account`	`uint principal`	`uint fee`	`uint amountIn`
`Burned`	`EtherWrapper`	`msg.sender`	The `amount` minus the `fee` (or the remaining reserves in the contract (`getReserves`).)	the fee in `sETH` that is deducted via the `burnFeeRate`	the total `amountIn`

Using native Ether (L1 only)¶

Destination contract (address & ABI): NativeEtherWrapper

Views¶

(Use EtherWrapper views above - the NativeEtherWrapper is simply a convenience contract that wraps ETH to WETH then forwards the WETH to the EtherWrapper)

Mint sETH with ETH¶

Methods¶

mint() payable

No Approval Requied

NativeEtherWrapper does not need approval to mint sETH as it accepts payable Ether

Events Emitted¶

For each mint, among other events, two will be emitted:

name	emitted on	`address account`	`uint principal`	`uint fee`	`uint amountIn`
`Minted`	`EtherWrapper`	`msg.sender`	The `amount` minus the `fee` (or the remaining `capacity` of the EtherWrapper if `amount` would reach the limit.)	the fee in `sETH` that is deducted via the `mintFeeRate`	the amount of Ether sent with the transaction (the transaction `value`)

name	emitted on	`address account`	`uint amountIn`
`Minted`	`NativeEtherWrapper`	`msg.sender`	the total `amountIn`

Example Transactions on Mainnet¶

NativeEtherWrapper.mint(1e18)

Burn sETH to ETH¶

Methods¶

burn(uint amount)

sETH Approval Required to Burn

NativeEtherWrapper needs to be approved to spend the user's sETH (as it needs to send it to itself in order to invoke EtherWrapper.burn())

Events Emitted¶

For each burn, among other events, two will be emitted:

name	emitted on	`address account`	`uint principal`	`uint fee`	`uint amountIn`
`Burned`	`EtherWrapper`	`msg.sender`	The `amount` minus the `fee` (or the remaining reserves in the contract (`getReserves`).)	the fee in `sETH` that is deducted via the `burnFeeRate`	the total `amountIn`

name	emitted on	`address account`	`uint amountIn`
`Burned`	`NativeEtherWrapper`	`msg.sender`	the total `amountIn`

Example Transactions on Mainnet¶

NativeEtherWrapper.burn(0.98e18)

Code Snippets¶

Exchanging ETH for sUSD

Synthetix JS (with ethers.js)

// npm install @synthetix/contracts-interface

// For node environments:
const { synthetix } = require('@synthetixio/contracts-interface');

// For others, see the contracts-interface README:
// https://github.com/Synthetixio/js-monorepo/tree/master/packages/contracts-interface
const provider = ethers.providers.getDefaultProvider('kovan');

// create a signer with a provider attached
const signer = new ethers.Wallet(
  // just a dummy kovan wallet with a little keth from the faucet
  '0xa0d951c494421559c63089093b020cf2f7aac003c916967dc36e989bc695222e',
  provider
);

// and then instantiate synthetix with the signer
const snxjs = synthetix({ network: 'kovan', signer });

(async () => {
  try {

  // mint 0.01 sETH via the NativeEtherWrapper
  const response = await snxjs.contracts.NativeEtherWrapper.mint({
    value: parseEther('0.01'),
    gasPrice: parseUnits('5', 'gwei'),
    gasLimit: 500e3,
  });
  console.log('Submitted', response.hash);

  await response.wait();
  console.log('Mined', `https://etherscan.io/tx/${response.hash}`);

})();

Solidity

pragma solidity 0.5.16;

import "synthetix/contracts/interfaces/IAddressResolver.sol";
import "synthetix/contracts/interfaces/IEtherWrapper.sol";

contract MyContract {

  // This should be instantiated with our ReadProxyAddressResolver
  // it's a ReadProxy that won't change, so safe to code it here without a setter
  // see https://docs.synthetix.io/addresses for addresses in mainnet and testnets
  IAddressResolver public synthetixResolver;

  constructor(IAddressResolver _snxResolver) public {
      synthetixResolver = _snxResolver;
  }

  function mintsETH() payable external {
    IEtherWrapper nativeEtherWrapper = synthetixResolver.requireAndGetAddress("NativeEtherWrapper", "NativeEtherWrapper is missing from Synthetix resolver");

    IEtherWrapper etherWrapper = synthetixResolver.requireAndGetAddress("EtherWrapper", "EtherWrapper is missing from Synthetix resolver");

    // this will be checked in the transaction below, but added here as an example
    require(etherWrapper.capacity() >= msg.value, "There isn't enough capacity left for this mint");

    // forward the ETH paid here to the native ether wrapper
    nativeEtherWrapper.mint.value(msg.value)();
  }

}

Tracking changes to parameters¶

There are three parameters in the EtherWrapper, which are managed by Synthetix governance and can be changed through the SCCP process (see SCCP-102 for a good example).

Parameter	Description
maxETH	the maximum amount of ETH held by contract
mintFeeRate	the fee for depositing ETH into the contract
burnFeeRate	the fee for burning sETH and releasing ETH from the contract

These can be tracked via listening to events on the SystemSettings contract:

name	emitted on	`uint maxETH`
`EtherWrapperMaxETHUpdated`	`SystemSettings`	The new maximum ETH cap of the wrapper.

name	emitted on	`uint rate`
`EtherWrapperMintFeeRateUpdated`	`SystemSettings`	The new mint fee rate
`EtherWrapperBurnFeeRateUpdated`	`SystemSettings`	The new burn fee rate