atimur / trueusd

The TrueUSD Smart Contracts

TrueUSD

This repository contains the TrueUSD ERC20 contract and related contracts.

The Contracts

This is a high-level overview of the contracts. For more specifics, see the relevant .sol files.

modularERC20/...

These contracts are inspired by and roughly equivalent to the corresponding ERC20 token contracts from OpenZeppelin. The main difference is that they keep track of balances and allowances by using separate contracts (BalanceSheet.sol and AllowanceSheet.sol) instead of mappings in their own storage. The ERCevents contract is used to ensure that events are still emitted from the original address even after the TrueUSD contract is delegated.

RedeemToken.sol

This makes it easier for users to burn tokens (i.e. redeem them for USD) by treating sends to 0x0 as burn operations.

BurnableTokenWithBounds.sol

This limits the minimum and maximum number of tokens that can be burned (redeemed) at once.

...Delegate....sol

If a new version of the TrueUSD contract is ever launched, these three contracts allow users to continue using the old version if they want and it will forward all basic transactions to the new one. See the section entitled Delegation Process below.

CompliantToken.sol

This ensures that only users who have passed a KYC/AML check can receive newly minted tokens or trade on certain restricted exchanges. It also allows for blacklisting of bad actors in accordance with the TrueCoin Terms of Use.

TokenWithFees.sol

This allows for transaction fees.

TrueUSD.sol

This is the top-level ERC20 contract tying together all the previously mentioned functionality.

TimeLockedController.sol

This contract is the initial owner of TrueUSD.sol. Consists of an Owner key, Mint Pause Keys, Mint Key, and Mint Approval Keys. It also imposes time delays on mint requests to maximize security.

MultiSigOwner.sol

This contract is the owner of TimeLockedController.sol. It turns every function that only the owner can access into a multisig function that requires 2/3 approvals.

Delegation Process

To delegate calls to new contract, first deploy a contract that implements DelegateBurnable. Configure fees, burn bounds, global pause etc. The contract must also implement setBalanceSheet(address) and setAllowanceSheet(address) in order to claim the storage contracts.

Set registry instance for the new contract. Set totalSupply to equal to the current totalSupply of the old contract.

Transfer ownership of the new contract to TimeLockedController. Claim ownership of new contract with TimeLockedController.

If the new contract has function setDelegatedFrom, call the function with TrueUSD contract address as the parameter.

call delegateToNewContract(_newContractAddress, _balanceSheetAddress, _allowanceSheetAddress) to delegate to new contract.

Testing

Initialize the registry submodule in the root directory:

• `git submodule init && git submodule update``

To run the tests and generate a code coverage report:

• npm install
• npm test

Other Information

Description	URL
Etherscan Page	https://etherscan.io/token/0x8dd5fbce2f6a956c3022ba3663759011dd51e73e
Coinmarketcap	https://coinmarketcap.com/currencies/true-usd/
TrueUSD’s Terms of Use	https://www.trusttoken.com/terms-of-use/

Social Links

Pages	URL
Website	https://www.trueusd.com/
Facebook	https://www.facebook.com/TrustToken/
Twitter	https://twitter.com/TrustToken
Telegram	https://t.me/joinchat/HihkMkTja1gIyBRM1J1_vg

Exchanges where TrueUSD is Traded

Exchanges	URL
Binance	https://www.binance.com/
Bittrex	https://bittrex.com
CoinTiger	https://www.cointiger.pro
Upbit	https://upbit.com/
HBUS	https://www.hbus.com/