stable-sl

Making easy to buy and sell crypto for people from Sierra Leone

Prototype running in production mode on https://stable-sl.pdJ.app and in development mode on https://stable-sl.pdJ.app:9001

Problem

In Sierra Leone few people manages a crypto wallet or an exchange and at the moment of this writing neither FonBnk nor MiniPay support Sierra Leone. Regargind exchanges only Binance and OKX operate there.

There are interesting saving and investment options in the web3, but this requires tools and education. We want to create tools and promote education about this in Sierra Leone.

Solution

• Building a webapp or app that will make easy to buy/sell stable crypto to the people of Sierra Leone.
• Educate in the usage of stable cryptocoins and saving and investment opportunities.
• Motivated by the initial Divvi offering of FonBnk as a possible backend protocol, in march 2025 we proposed to FonBnk to be their partners in Sierra Leone. Later they told us that they already had a team there, but up to now they still don't support the currency, neither payment methods of Sierra Leone not even in their sandbox.
• So at least while FonBnk or another group offers an on-ramp/off-ramp solution we have started building one, operating with a team based on the Mission Hope School located in Kabala (the school is lead by the pastor Zechariah Conteh who is in the team).

Location of Impact

Sierra Leone

Contents of this monorepo

This monorepo includes:

1. The frontend to interact with the customers that initially can run as a web application.
2. The APK of the Gateway application that runs in our phone to manage transactions.

Running the frontend in development mode

The frontend is better served in SSL with nginx. See detailed instructions in packages/react-app/README.md

Design

Architecture

The architecutre is presented in the following diagram:

Authentication

• For the customer - coordinator backend we use a randomly generated authentication token.
• For the coordinator - gateway we want to use a shared secret only between them both to encrypt the messages

Sequence diagram for on-ramping


Sequence diagram for off-ramping


Status of Implementation

It is a prototype that:

1. Has fully functional on-ramp with USDT and GoodDollar
2. Shows how off-ramp works with USDT and GoodDollar
3. Still doesn't use an API for quotes, we set buying and selling prices manually and adjust periodically (that makes sense given the stability of SLE)
4. It interacts with the gateway receiving the SMS with Orange Money notifications --a method that has to be improved.
5. The on-ramp version in production can make payments in mainnet in USDT or GoodDollar limited to small amounts. The development version runs on Alfajores and makes payments in Mock USDT and Mock GoodDollar (deployed by us).