# Developer Docs

## Getting Started

These docs are a comprehensive guide to the Rifi protocol, based on the Rifi Whitepaper (May 2021).

### Networks

The Rifi Protocol is currently deployed on BSC Mainnet:

Contract | ABI | Address |
---|---|---|

rUSDC rToken | JSON | 0x916e87d16B...cf3B5C11f5 0x916e87d16B2F3E097B9A6375DC7393cf3B5C11f5 |

rUSDT rToken | JSON | 0x383598668C...f18D311063 0x383598668C025Be0798E90E7c5485Ff18D311063 |

rBUSD rToken | JSON | 0x6db6A55E57...988666553A 0x6db6A55E57AC8c90477bBF00ce874B988666553A |

rBTC rToken | JSON | 0x53aBF990bF...cF8bdF11eB 0x53aBF990bF7A37FaA783A75FDD75bbcF8bdF11eB |

rDAI rToken | JSON | 0x9B9006cb01...b37d8bC078 0x9B9006cb01B1F664Ac25137D3a3a20b37d8bC078 |

RIFI | JSON | 0xe17fbdf671...f4245a3ffe 0xe17fbdf671f3cce0f354cacbd27e03f4245a3ffe |

Cointroller | JSON | 0x4f3e801Bd5...21d31F64e4 0x4f3e801Bd57dC3D641E72f2774280b21d31F64e4 |

Price Feed | JSON | 0xD55f01B4B5...70A1a9DBa5 0xD55f01B4B51B7F48912cD8Ca3CDD8070A1a9DBa5 |

### Protocol Math

The Rifi protocol contracts use a system of exponential math, Exponential.sol, in order to represent fractional quantities with sufficient precision.

Most numbers are represented as a mantissa, an unsigned integer scaled by 1 * 10 ^ 18, in order to perform basic math at a high level of precision.

#### rToken and Underlying Decimals

Prices and exchange rates are scaled by the decimals unique to each asset; rTokens are BEP-20 tokens with 8 decimals, while their underlying tokens vary, and have a public member named decimals.

rToken | rToken Decimals | Underlying | Underlying Decimals |
---|---|---|---|

rUSDC | 8 | USDC | 18 |

rUSDT | 8 | USDT | 18 |

rBUSD | 8 | BUSD | 18 |

rBTC | 8 | BTC | 18 |

rDAI | 8 | DAI | 18 |

#### Interpreting Exchange Rates

The rToken Exchange Rate is scaled by the difference in decimals between the rToken and the underlying asset.

Here is an example of finding the value of 1 rUSDT in USDT with Web3.js JavaScript.

To find the number of underlying tokens that can be redeemed for rTokens, multiply the number of rTokens by the above value oneRTokenInUnderlying.

#### Calculating Accrued Interest

Interest rates for each market update on any block in which the ratio of borrowed assets to supplied assets in the market has changed. The amount interest rates are changed depends on the interest rate model smart contract implemented for the market, and the amount of change in the ratio of borrowed assets to supplied assets in the market.

Interest accrues to all suppliers and borrowers in a market when any address interacts with the market’s rToken contract, calling one of these functions: mint, redeem, borrow, or repay. Successful execution of one of these functions triggers theaccrueInterest method, which causes interest to be added to the underlying balance of every supplier and borrower in the market. Interest accrues for the current block, as well as each prior block in which the accrueInterest method was not triggered (no user interacted with the rToken contract). Interest rifis only during blocks in which the rToken contract has one of the aforementioned methods invoked.

Here is an example of supply interest accrual:

Alice supplies 1 USDT to the Rifi protocol. At the time of supply, the supplyRatePerBlock is 37893605 Wei, or 0.00000012 USDT per block. No one interacts with the rToken contract for 3 blocks. On the subsequent 4th block, Bob borrows some USDT. Alice’s underlying balance is now 1.00000050 USDT (which is 37893605 Wei times 4 blocks, plus the original 1 USDT). Alice’s underlying USDT balance in subsequent blocks will have interest accrued based on the new value of 1.00000050 USDT instead of the initial 1 USDT. Note that the supplyRatePerBlock value may change at any time.

#### Calculating the APY Using Rate Per Block

The Annual Percentage Yield (APY) for supplying or borrowing in each market can be calculated using the value of supplyRatePerBlock (for supply APY) or borrowRatePerBlock (for borrow APY) in this formula:

Here is an example of calculating the supply and borrow APY with Web3.js JavaScript:

### Gas Costs

Function | Typical Gas Cost |
---|---|

Mint | < 150K |

Redeem, Transfer | < 250K if borrowing, otherwise < 90K |

Borrow | < 300K |

Repay Borrow | < 90K |

Liquidate Borrow | < 400K |

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