What is USR Token?

[zjuchenyuan]

Info: current mainnet eth block number: 11210219

I'm wondering where the interest come from, so I made some investigations for dUSDx:

The contract address for dUSDx is 0x109917f7c3b6174096f9e1744e41ac073b3e1f72 etherscan, and it has two handlers:

• InternalHandler deployed at 0x885dd179c76ee5949b9053f1958ba3a91e4cf592, proxy for 0x3c573234e1a9e47e0cac56db543e1ca153eb7f8b
• USRHandler deployed at 0x8916a9b0064feab04b3bf3729adbb0be119ed12d, proxy for 0xbde39e19dc806620d5377cd14827d42bbe42c8f9, whose underlying USR address is 0xef004c5cdfaab19299b3ed66f14ec010fe5f20d0, proxy for 0xd4eef282f58ecaf12118e96ed4c06f60f88009c6, which NEED decompile

The code for calculating exchange ratio, namely how many USDx can 1 dUSDx exchange, is getCurrentExchangeRate, which is implemented by summing up the handlers' getRealBalance(_token) and then divided by totalSupply

dToken/contracts/DToken.sol

Lines 357 to 377 in 563d7d0

	function getCurrentExchangeRateByHandler(
	address[] memory _handlers,
	address _token
	) internal returns (uint256) {
	uint256 _totalToken = 0;
	// Get the total underlying token amount from handlers
	for (uint256 i = 0; i < _handlers.length; i++)
	_totalToken = _totalToken.add(
	IHandler(_handlers[i]).getRealBalance(_token)
	);
	// Reset exchange rate to 1 when there is no dToken left
	uint256 _exchangeRate = (totalSupply == 0)
	? BASE
	: rdiv(_totalToken, totalSupply);
	require(_exchangeRate > 0, "Exchange rate should not be 0!");
	return _exchangeRate;
	}

By calling getBaseData for different blocks (using MetaMask API), I find that getCurrentExchangeRate update for each block:

def getbasedata(id, blockid):
    data = '{"id":%d,"jsonrpc":"2.0","method":"eth_call","params":[{"data":"0x148a95ea","to":"0x109917f7c3b6174096f9e1744e41ac073b3e1f72"},"%s"]}'%(id, blockid)
    response = sess.post('https://mainnet.infura.io/v3/9aa3d95b3bc440fa88ea12eaa4456161', headers=headers, data=data)
    res = response.json()
    #print(res)
    data = base64.b16decode(res["result"][2:].upper())
    i = 1
    rate = int.from_bytes(data[i*32:i*32+32],"big")
    return rate

>>> getbasedata(1,hex(11210217))
1008824037259265003
>>> getbasedata(1,hex(11210218))
1008824072639567928
>>> getbasedata(1,hex(11210219))
1008824108020446490

The InternalHandler's getRealBalance can be easily called via etherscan dapp getRealBalance 0xeb269732ab75a6fd61ea60b06fe994cd32a83549

And this output seems stable 83373969497199741501815, not change for hours. So this is not the source of interest.

However, I cannot find way to call USRHandler's getRealBalance, and the implementation code is not available on Etherscan.

So, my question is:

• What is USR Token?
• Where can I find the implementation of USR Token, i.e. the code for contract 0xd4eef282f58ecaf12118e96ed4c06f60f88009c6
• Where does the interest come from, and why this is updating for every block? I guess the calculation involves block number?

Thanks for your answering~

[zjuchenyuan]

Ok, I find the souce code of USR: https://github.com/dforce-network/USR

And the description for USR: https://zhuanlan.zhihu.com/p/222323344

USR（USDxSaving Rate）是USDx全局利息。USR上线后，USDx将成为第一个支持系统性存款收益的法币型稳定币（100%法币型稳定币储备）。用户将USDx存入USR合约即可获得存款利息，操作便捷，随存随取。USR的利息主要来源于USDx的底层成分稳定币，用户铸币时，存入的成分稳定币将自动转换为dToken并存入生息市场，目前，成分币获得的利息将100%分配给USR。用户将USDx存入USR即可获得系统性利息收入。

The initialize call transaction is 0xb6961ea4588cc4f9e78161c9c025970514ebb24ca024258887c3d6283fcf7b93, which set _underlyingToken as USDx, and set _interestProvider as 0x2Cd4E8D82f62a91b2299B083Ba08532A6A96a13a, which is again is a USRProxy for 0x47992aaada10c4b55659ff5e4d95527b8d50e434.

So the question becomes:

• Where is the implementation of 0x47992aaada10c4b55659ff5e4d95527b8d50e434 ?
• From which markets do USR get interest?

[zjuchenyuan]

Continue searching, I find the implementation of 0x47992aaada10c4b55659ff5e4d95527b8d50e434 should be InterestProvider.sol, key code:

https://github.com/dforce-network/USR/blob/701ebd9d93224856f2144c871edc45f84d7cfd05/contracts/InterestProvider.sol#L174-L186

    function getInterestAmount() external returns (uint256) {
        InterestLocalVars memory _local;

        _local.xTokens = IDFStore(dfStore).getMintedTokenList();
        _local.dfPool = dfPool;
        for (uint256 i = 0; i < _local.xTokens.length; i++) {
            (, _local.xInterest) = IDFPoolV2(_local.dfPool).getInterestByXToken(
                _local.xTokens[i]
            );
            _local.xTotalInterest = _local.xTotalInterest.add(_local.xInterest);
        }
        return _local.xTotalInterest;
    }

And corresponding dfStore is set by transaction 0x9d21785853478c39ef39027d2b2a5e43b21e5fd0d3fb9815c9a40a439892460d to 0xd30d06b276867cfa2266542791242ff37c91ba8d (second parameter of initialize call).

According to etherscan of dfStore The getMintedTokenList will return 0x26472cc7f4cb43ae9b3f18c705de8c34578933f9, 0x666ed86f5ed0e80d8f441002b1ae08dcbaeff1e6, 0x284bfce387b079eb3461d7da9399266662e697c5, 0x369dffbb1d8f49ecf63501e2d175742ae1bfdfc8

Contract 0x26472cc7f4cb43ae9b3f18c705de8c34578933f9 has SUSHI and DAI, which I know can earn from liqudity mining. However, the other 3 contracts has no ERC-20 Tokens, how can them provide interest?

And where can I find the source code for these MintedTokenList tokens?

Specifically, where is the implementation of function getInterestByXToken?