Remora

Inspiration

Storage providers (SPs) have to post $FIL collateral to onboard network storage capacity and accept storage deals. This collateral incentivizes the storage provider to behave correctly, by presenting timely proofs of the health of the data (PoRep, PoSt), or they risk getting slashed. While important, the need to pledge collateral creates friction and an immediate barrier that throttles SP participation and growth. On the other hand, the Filecoin network has a large base of long-term token holders that would like to see the network grow, and are willing to lend their FIL to reputable and growth-oriented SPs. A lending protocol can solve this issue. Storage providers can borrow collateral from lenders and the smart contract will lock the future income until the storage providers have repaid their loan.

Remora allows a user with liquidity to lend out his $FILs and enhance the network and an SP to borrow collateral-free $FILs and become an SP (or improve its $FIL collateral) by repaying his debt through the rewards it gets from his storage-providing activity.

The idea comes from the following: https://fvm-forum.filecoin.io/t/lending-pool-cookbook/114

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What it does

Remora is a collateral-free $FIL lending and borrowing protocol to facilitate network storage providing. Remora works following an order book model where lenders create loan positions making $FIL available with a certain interest rate and borrowers can take a designated amount based on pledging and collateral requirements in offering computer storage services.

The borrower must repay its debt and the loan interest through the rewards it gets from its storage-providing activity.

Under the hood, Remora smart contracts interact with the built-in Miner Actor using Filecoin Solidity API libraries.

Smart contract

There are two smart contracts:

• LenderManager -> 0x3f06D24C8F7F6E1eE99Db84A03b3563C89345A05
• Escrow

LenderManager is the core of our lending/borrowing protocol. It is a singleton contract that allows lenders to create lending positions and borrowers to fill them. The contract keeps track of all operations.

When a borrower wants to borrow $FILs, funds are transferred from the LenderManager contract to a new Escrow contract. The LenderManager acts as a factory, using the CREATE2 operation to clone and deploy the Escrow contract for each loan. The Escrow contract is where the $FILs are sent when a borrower takes out a loan.

Before allowing a borrower to take a loan, the LenderManager verifies their reputation using the Filecoin Reputation API (https://filrep.io/api). The API are called using a custom oracle we built for the hackathon.

Once the Escrow contract is deployed, the borrower must set this contract as the owner and beneficiary of their Miner actor. The Escrow contract then confirms it is the owner and beneficiary of the Miner actor. Once confirmed, Escrow sends all $FIL to the Miner actor and the storage provider can begin their activity on the Filecoin blockchain.

A note for the Miner actor

During the hackathon, we encountered multiple issues using the Filecoin Solidity API. We decided to switch to the mock API. As such, we simulated the behavior of the Miner actor customizing the MinerMockAPI.sol smart contract provided by the library.

Backend

The backend built on Lambda is used to implement the Miner reputation control. Specifically, the LenderManager smart contract provides a checkReputation function that takes a Miner Actor address as input and emits the checkReputation(uint256 requestId, uint256 response) event. The backend is listening for the event and does a check of the Miner Actor using the filrep API (https://filrep.io/api). Once checked, the backend calls receiveReputation on the LenderManager smart contract writing the Miner Actor's reputation (Not found, Bad reputation, or Good reputation) on the chain storage. The diagram below visualizes the workflow.

UI Prototype

Using the demo website $FIL holders can create their own Lending position and storage providers can borrow $FIL. Both a Lender and a Borrower have their own positions page where they can make management operations such as: repay the debt through periodic rates, close loan and move $FIL from/to the Miner Actor. The UI makes contract calls, read from FEVM events, and interacts with the backend for the Miner reputation check.

The Lido Frontend template (adapted for Filecoin FEVM) was a great starting point. The Frontend is built using React js. The frontend was deployed using Spheron Network.

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Built with

• Filecoin Solidity API (https://github.com/Zondax/filecoin-solidity)
• Filecoin reputation API (https://filrep.io/api)
• Hardhat (https://hardhat.org/)
• React js
• Next js
• AWS Lambda

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Challenges we ran into

Filecoin Solidity API:

The biggest challenge has been to study and understand how a node that acts as a storage provider works and then build our application using the Filecoin Solidity APIs that allow us to interact with built-in Actors. The libraries are very powerful however we encountered great challenges in using the libraries such as a lack of documentation and some errors while testing calls. Other than these, using Filecoin Solidity libraries is quite complex because you need to learn first how the Filecoin architecture works.

Understanding the Filecoin Miner's operation:

We needed to understand how a Miner node works especially the wallets interacting with the miner such as Owner, Beneficiary, and Worker wallets. Then we studied how the economic model works in particular how the collateral pledge, network slashing conditions, and Storage provider rewards work in order to build a working POC.

FEVM and Filecoin Network's distinctive features:

A great challenge was to understand how the FEVM works by interacting with the Filecoin network such as F addresses and EVM addresses and how to convert them.

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What we learned

We have learned so much over the course of the hackathon. Few big things

• How FEVM works and differences with EVM
• How the FEVM interacts with the functionality of the Filecoin network (especially the built-in Actors)
• Using Filecoin Solidity API
• Understanding more about how Lotus nodes work
• Storage providers economy on the Filecoin network