dexadexa/dexa

USSD & WhatsApp Global south last mile Hedera access in Africa (No internet or very low bandwidth internet) # DeXa — USSD & WhatsApp Hedera Last‑Mile Access in the Global South 📄 View the Pitch Deck (PDF) 📄 View the Developer Certificate (PDF) DeXa brings Hedera (EVM) to people with no internet or very low bandwidth by using familiar channels: USSD and WhatsApp. The project enables secure wallet creation, balance checks, and payments using simple menus (USSD) or natural language chat (WhatsApp), with multi‑language support and low fees on Hedera Testnet/Mainnet. --- ## Repository layout - `ussd/` — Vite + React UI for showcasing the USSD/SMS experience and related assets. Includes a placeholder backend folder for USSD/SMS gateways. - `whatsapp/` — TypeScript Node service integrating Twilio WhatsApp, Prisma/PostgreSQL, and Hedera EVM (ethers v6). Includes tests and simple contract tooling. --- ## Key capabilities - USSD wallet flows: create, view, secure, delete (PIN protected) - SMS/NLP assistant for blockchain queries and actions - WhatsApp payments: P2P, phone-based identity mapping, group payments, refunds (WIP) - Multi‑language UX (e.g., English, French, Kiswahili) - Hedera EVM settlement (HBAR), very low fees, rapid finality --- ## System Architecture ``` ┌───────────────────────┐ ┌────────────────────┐ │ Feature phone user │ │ Smartphone user │ │ (USSD/SMS) │ │ (WhatsApp) │ └──────────┬────────────┘ └─────────┬──────────┘ │ USSD/SMS │ WhatsApp ▼ ▼ ┌──────────────────────────────┐ ┌─────────────────────────┐ │ USSD/SMS Gateway │ │ Twilio WhatsApp API │ │ (e.g., Africa's Talking) │◄───────────►│ (webhooks + outbound) │ └──────────┬───────────────────┘ └──────────┬──────────────┘ │ HTTP (USSD callbacks) │ Webhook POST ▼ ▼ ┌───────────────────── …