TrueUSD

This repository contains the TrueUSD ERC20 contract and related contracts. For a high-level overview, see this video.

TrueUSD.sol

TrueUSD.sol is the main ERC20 contract. It inherits the following from OpenZeppelin's open source standard token contracts:

1. standard ERC20 functionality
2. burning tokens
3. pausing all ERC20 functionality in an emergency
4. transferring ownership of the contract

Additionally, it adds the following features:

Whitelists

In order to deposit USD and receive newly minted TrueUSD, or to burn TrueUSD to redeem it for USD, users must first get onto the corresponding whitelists (AddressList.sol) by going through a KYC process (which includes proving they control their ethereum address using AddressValidation.sol).

Blacklist

Addresses can also be blacklisted, preventing them from sending or receiving TrueUSD. This can be used to prevent the use of TrueUSD by bad actors in accordance with law enforcement. The blacklist will only be used in accordance with the TrueCoin Terms of Use.

Insurance Fees

The contract is equipped to charge transaction fees upon minting, burning, and/or transferring of TrueUSD. There is currently a 7 bips fee on transfers. These fees are intended to compensate whomever is insuring the contract. With the launch of the TrustToken platform, TrustToken holders will stake TrustToken so that if anything were to go wrong with the USD backing (e.g. a bank holding the funds goes under), TrueUSD holders would be compensated from the TrustToken stake instead.

Delegation to a new contract

If TrueUSD.sol ever needs to be upgraded, the new contract will implement the interface from DelegateERC20.sol and will be stored in the 'delegate' address of the TrueUSD contract. This allows all TrueUSD ERC20 calls to be forwarded to the new contract, to allow for a seamless transition for exchanges and other services that may choose to keep using the old contract.

TimeLockedController.sol

This contract allows us to split ownership of the TrueUSD contract into two addresses. One, called the "owner" address, has unfettered control of the TrueUSD contract - it can mint new tokens, transfer ownership of the contract, etc. However to make extra sure that TrueUSD is never compromised, this owner key will not be used in day-to-day operations, allowing it to be stored at a heightened level of security. Instead, the owner appoints an "admin" address. The admin can do most things the owner can do, and will be used in everyday operation. However, for critical operations like minting new tokens or transferring the contract, the admin can only perform these operations by calling a pair of functions - e.g. requestMint and finalizeMint - with (roughly) 24 hours in between the two calls. This allows us to watch the blockchain and if we discover the admin has been compromised and there are unauthorized operations underway, we can use the owner key to cancel those operations and replace the admin.

AddressList.sol / AddressValidation.sol

See "Whitelists" and "Blacklist" above.

DelegateERC20.sol

See "Delegation to a new contract" above.