Skip to content

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

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

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

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

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

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
// 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}`);

})();
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
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