Village Vault: Offline Community Savings & Lending Rings

In many communities, informal savings groups (tontines, susu, chit funds) are the only financial safety net. Village Vault is a complete system to manage such groups without needing internet, a bank account, or a smartphone. The core is a ruggedized, low-cost device (Raspberry Pi with small e-ink screen, powered by solar or battery) carried by a group organizer. Members interact via NFC cards or simple number pads. All transactions are recorded cryptographically on a local blockchain (not public, just a distributed ledger across multiple organizers' devices). If the group organizer's device fails, another member's device can reconstruct the ledger via peer-to-peer sync when they are in close proximity (e.g., at market). The system ensures transparency, prevents disputes, and can handle arbitrary contribution schedules, loans with interest, and dividend distributions. The ambition is to replace paper ledgers and reduce fraud, all while being fully offline and affordable (target cost per device $50).

In rural areas and informal economies, savings groups are ubiquitous but plagued by record-keeping errors, lack of transparency, and theft. Existing digital solutions require smartphones and internet, which are often scarce or expensive. Traditional paper records can be lost or manipulated. There is a need for a robust, low-cost, offline tool that strengthens trust and efficiency in community banking.

• Develop a durable, solar-rechargeable device that can operate months without external power.
• Create a cryptographic ledger that can be verified and synced via local wireless (e.g., LoRa or Bluetooth mesh) without internet.
• Design a simple user interface using text and icons on e-ink screen, with input via simple buttons or NFC.
• Enable group creation, contribution recording, loan disbursal, and balance inquiries.
• Ensure data redundancy: any two devices in a group can reconstruct the full ledger.

• Not aiming to connect to internet or cloud for any core functionality; optional sync to a 'town hall' device for aggregated reporting.
• Not trying to replace all financial needs; just savings circles.
• Not requiring government IDs or formal KYC; pseudonymous member IDs based on NFC token.
• Not aiming for high transaction throughput; designed for groups of up to 50 members.

• Hardware: Raspberry Pi Zero 2W (or RP2040 for lower cost), 2.9" e-ink display, solar charging circuit (6V 100mA panel, LiFePO4 battery), LoRa module (RFM95) for local mesh, NFC reader (PN532), tactile buttons, rugged enclosure.
• Software: MicroPython or C on RTOS, custom lightweight DAO-like ledger (append-only log of signed transactions), AES-128 encryption for member data, Ed25519 for signatures.
• Mesh protocol: LoRaWAN-like (but private local network) for periodic sync, using a gossip protocol when devices are within 1 km range.

Each device is a node in a mesh network that maintains a copy of the entire group ledger. Transactions are created offline on a device (e.g., member Alice gives money to treasurer Bob, who records it). The transaction is signed by both parties via their NFC cards and the device's private key. Once signed, the transaction is broadcast over LoRa to all nearby devices in the mesh. Other devices verify and append to their local copy. If a device is out of range, it will receive transactions when it next comes within range of another device. The ledger is a chain of blocks, but not proof-of-work; security relies on signatures and the fact that all members have a copy. Disputes are resolved by majority consensus among the devices in the mesh. For disaster recovery, a full backup is printed as a QR code page or saved on a microSD.

• Hardware failure: relying on low-cost components may lead to early failure; need robust testing.
• Security: offline mesh can be jammed or spoofed; need encryption and authentication.
• User adoption: community members may be skeptical of technology; need extensive training and trust built with local leaders.
• Regulatory: informal savings groups may be illegal or scrutinized in some countries; need to be aware of local laws.

• Should we use a blockchain at all, or just a signed audit log? Simpler signature-based may be better than full blockchain.
• How to handle membership changes (adding/removing members) without internet?
• What tier of mesh range is achievable? 100m? 1km? Need to test LoRa in village settings.

I was working on this during my free evenings after a community banking project in Kenya, but then I got a promotion that left me no hobby time. The codebase is half-written on a GitHub private repo; the hardware prototype worked on my desk but never got field-tested. It's a plan I still believe in, but it's on the shelf for now.

This project was inspired by 'PieDAV' and 'M-Pesa' but fully offline. The name 'Village Vault' is a working title. I've talked to NGOs who are interested but wanted a more mature prototype. Someday.