Backing Asset: USDM
Last updated
Last updated
USTB is 100% backed by another stablecoin, USDM.
The following content in this section has been taken directly from the , with permission from the team. Please refer to the Mountain Protocol docs for the latest information.
USDM is built on top of the OpenZeppelin implementation, adding rebasing dynamics to the contract, following the same "share of total supply" pattern as .
The rebasing mechanism is implemented via the "shares" concept. Instead of storing a map with account balances, the USDM smartcontract stores which "share" of the total pool is owned by the account. The balance of an account is calculated as follows:
shares - map of account share of the total supply. Every time USDM is minted or burnt, it is converted to shares and added/deducted and assigned to user's balance.
rewardMultiplier - is the sum of daily addRewardMultiplier, accruing daily for users.
If a user purchased 100 USDM when the rewardMultiplier was 1.00, that user would receive 100 shares of USDM. If the average APY for the year stayed constant at 5%, that user would now have 105 USDM. Below is an example of the USDM balances, shares, and rewardMultiplier:
Day 0
1
Day 365
1.05
If this user wanted to redeem 100 of the 105 USDM, they could transfer 100 USDM to their Mountain Protocol account, via the Platform.
Under the hood, the contract will transfer 100/1.05 = 95.238 shares
In this example, the user will receive $100 for their 100 USDM and keep 5 USDM.
The rewardMultiplier variable is updated daily, at or around 12pm UTC, by calling the addRewardMultiplier function applying the daily yield, changing the value of the rewardMultiplier.
Below is an example of how the rewardMultiplier and the addRewardMultiplier work together (note that USDM contract runs on an 18-digit standard, but those have been simplified for this example). The rewardMultiplier starts at one and is increased by the addRewardMultiplier function on a daily basis.
The column shows the value of the rewardMultiplier sent to the addRewardMultiplier function and the resulting ongoing state of rewardMultiplier.
0
1
0.000080986
1
1.000080986
0.000080993
2
1.000161979
0.000081000
3
1.000242979
0.000081006
4
1.000323985
0.000081012
5
1.000404997
6
...
transfer: The transfer function works like any other ERC20. Note that the transferred amount will be USDM, not shares. This will match the user expected behavior, by sending balanceOf and not Shares.
totalShares: This function returns the total number of shares in circulation. Note that this number will be different from the total USDM in circulation, as this does not account for the yield component embedded in the rewardMultiplier.
totalSupply: This function returns the total number of USDM in circulation. totalSupply is calculated by applying the rewardMultiplier to the totalShares.
The USDM contract builds its foundation on top of OpenZeppelin Contracts library, widely used and recognized battle-tested components throughout the Ethereum ecosystem:
AccessControlUpgradeable.sol
PausableUpgradeable.sol
UUPSUpgradeable.sol
CountersUpgradeable.sol
ECDSAUpgradeable.sol
EIP712Upgradeable.sol
IERC20PermitUpgradeable.sol
IERC20MetadataUpgradeable.sol
Explore the following essential resources to gain a comprehensive understanding of USDM Token and its associated network:
Below you will find the access control roles and their corresponding addresses for USDM. Each role is linked to a specific set of permissions that are associated with it.
MINTER_ROLE: Grants the ability to mint tokens.
0x48AEB395FB0E4ff8433e9f2fa6E0579838d33B62
BURNER_ROLE: Grants the ability to burn tokens.
0x48AEB395FB0E4ff8433e9f2fa6E0579838d33B62
BLOCKLIST_ROLE: Grants the ability to manage the blocklist.
0xB4d98351418c3d35195406e114E56B068F876c8f
ORACLE_ROLE: Grants the ability to update the reward multiplier.
0xD20D492bC338ab234E6970C4B15178bcD429c01C
PAUSE_ROLE: Grants the ability to pause/unpause the contract.
0x16d72b58B8A0bBCf3A6751920ef127Fe746a3BB0
UPGRADE_ROLE: Grants the ability to upgrade the contract.
Not assigned
DEFAULT_ADMIN_ROLE: Grants the ability to grant or revoke roles.
0x313d5B7EfDcd84e8a52D425282B03860e9354d74
To solve this problem and ensure USDM holders have full compatibility with DeFi without giving up their rewards, the Mountain Protocol team has built a wrapper on USDM which is called wUSDM. Such wrapper is very similar to Lido's wstETH, a product that is already familiar to the digital asset ecosystem.
rewardMultiplier: Allows developers to read the cumulative yield accrued since the beginning of the contract. Note that past does not predict future. The is usually a better proxy to USDM yield than historic values.
USDM Ethereum Mainnet Token Address:
wUSDM Ethereum Mainnet Token Address:
Open Source Code:
Bug Bounty Program:
Audit Reports:
Security Center by OpenZeppelin:
Security Policy:
License:
Smart Contract Code Coverage:
Documentation:
Acknowledging the complexities of handling rebasing tokens in the DeFi ecosystem, the contract serves as a wrapped token, simplifying integration while preserving stability.
The wUSDM contract is an ERC-4626 (following the , leveraging the ), enabling users to deposit USDM in exchange for wUSDM tokens. The USDM tokens are rebasing, whereas the wUSDM tokens are non-rebasing, making wUSDM easier to integrate in DeFi protocols.
Rebasing tokens have known integration challenges with protocols that assume constant balanceOf for tokens (such as Uniswap, 1Inch and Sushiswap). This can lead to daily rewards being captured by players other than the USDM holders in protocols. The stETH issuer, Lido, has .