User App Demo: bangla-coin-sust.vercel.app
010000000001, 010000000002 are agent accounts. Account with any other phone number is a regular user account. The default OTP is 123456.
Video Presentation and Project Document: https://drive.google.com/drive/folders/1qRZsYYU4KDS6i1sEx78BtwdCKXHmdW8M
Instant payments are convenient, but they are a paradise for scammers. We have introduced Friction to inherently protect users from losing their life savings. We implemented a decentralized money transaction system using Blockchain technology, along with an intelligent Risk Engine where high-risk transactions trigger a mandatory blockchain-enforced delay. Unlike other services that run on a single central server, we built a Distributed Validator Network where all independent nodes must reach consensus before any transfer is committed. This eliminates the monopoly of banks and services like bKash, enabling lower transaction fees through a multi-validator, miner-like architecture. We prioritize human safety over raw transaction speed. Our motto is to make money transactions secure and reliable — a system where instantaneity is not the first priority.
Bangla Coin is an innovative, Friction-First Web3 platform designed to combat scams and fraud through dynamic transaction delays. Unlike traditional blockchains where transactions are instant and irreversible, Bangla Coin introduces a smart "Friction Engine" that slows down high-risk transfers, giving users a window to cancel suspicious transactions before they are finalized on the blockchain.
In the rapidly evolving digital landscape of Bangladesh, speed has often been the primary metric for financial success. However, the rise of "instant" mobile financial services has inadvertently fueled a parallel surge in digital fraud, social engineering scams, and accidental transfers. Bangla Coin, developed by Team SUST SONGLAP, introduces a paradigm shift: Friction-First Finance. By prioritizing security over velocity, Bangla Coin provides a robust, blockchain-backed solution designed to protect every Taka.
The core usage of Bangla Coin revolves around its Dynamic Risk Engine. Unlike traditional apps that process payments in milliseconds, Bangla Coin evaluates every transaction against six specific risk rules.
For a daily user, the experience is intuitive yet protective. When sending money to a verified family member, the "friction" is minimal—perhaps a 10-second countdown. However, if a user attempts to send a large sum to a first-time recipient or a wallet flagged by the community, the system automatically escalates the delay to the 180-second maximum. This critical "cool-down" period allows users to catch mistakes or realize they are being scammed before the funds are permanently committed to the blockchain.
Agents play a vital role in the ecosystem, serving as the bridge between physical cash and digital Bangla Coins. Using the Agent Cash-In feature, users can convert BDT into digital assets securely.
Furthermore, the Community Wallet (DAO) functionality allows groups—such as student organizations or small businesses—to manage collective funds. Usage here is democratic: a member proposes a spend, and the funds only release once a majority of the group votes "Yes" on-chain.
The primary benefit of Bangla Coin is the mitigation of financial loss. By making "slow money" a feature, the platform effectively kills the "urgency" tactic used by scammers.
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Data Safty using Blockchain: Once a transaction passes BFT consensus across all the validators, it is written simultaneously to every chain copy as a cryptographically hashed block — each block containing the fingerprint of the previous one, so altering any past record breaks the entire chain and is immediately detected. With all independent copies, a hacker would need to compromise more than 50% nodes at once to succeed, which the consensus mechanism prevents by flagging and isolating any diverging node and force-syncing it back to the clean ledger automatically.
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Fraud Deterrence via "Vote to Ban": The decentralized network of Validator Nodes acts as a digital jury. If a transaction appears fraudulent, validators can vote to ban it, preventing the movement of stolen funds. This collective oversight provides a layer of security that centralized systems often struggle to replicate in real-time.
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Immutable Transparency: Every transaction is recorded on a SHA-256 hash-linked ledger. For the user, this means an indisputable, permanent record of their financial history that cannot be altered or deleted by any central authority.
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Empowerment through DAOs: For rural communities and small cooperatives in Bangladesh, the DAO feature eliminates the "trusted middleman" problem. It ensures that no single individual can vanish with group savings, as the smart contract enforces collective permission for every withdrawal.
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Resilience and Reward: By running on a Permissioned Proof-of-Authority (PoA) chain, the system remains energy-efficient and fast enough for high-volume use while rewarding the distributed validators who provide the computational power to keep the network alive.
In summary, Bangla Coin is not just a payment tool; it is a safety net. It empowers the citizens of Bangladesh to embrace blockchain technology with the confidence that their hard-earned money is protected by the very code that moves it.
| Attribute | Detail |
|---|---|
| Project Name | Bangla Coin |
| Hackathon | Friction Hackathon 2026 |
| Team | SUST SONGLAP |
| License | MIT (Fully Open Source) |
| Chain Type | Permissioned PoA (Hardhat local → Polygon Mumbai testnet) |
| Peg | 1 Bangla Coin = 1 BDT (Fully collateralized) |
| Max Delay | 1 minutes (60 seconds, enforced on-chain) |
| MVP Scope | 72-hour hackathon build |
| Signup Page | Login Page |
|---|---|
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The central hub for managing BDT balances and viewing transaction history.
A live visualization of the on-chain delay enforced by the risk engine.
These screens demonstrate the decentralized governance of group funds.
| Wallet Overview | Proposal Approval |
|---|---|
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| Node Status | Node Admin |
|---|---|
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The 48-hour build focuses on eight core features. All other functionality is deferred to Phase 2+.
- F1 — Wallet & Balance: Phone-based login (OTP), custodial encrypted keys, BDT balance display, and transaction history.
- F2 — Transactions with Friction Timer: A risk engine scores transactions, returning a delay of 10s – 3m. A live countdown is displayed before execution.
- F3 — Vote to Ban (Validators): If a majority of validator nodes flag a transaction as suspicious, it is rejected before finality.
- F4 — Community Wallet (DAO): Group wallets where funds release only after a majority approval vote on-chain.
- F5 — Emergency Freeze: A "one-tap" lock button that cancels all pending transactions. Requires a PIN to unfreeze.
- F6 — Immutable Transaction Log: A SHA-256 hash-linked ledger with a basic block explorer to verify the chain of hashes.
- F7 — Agent Network: Authorized agents can perform "Cash-In" for users and maintain cash equilibrium via the agent network.
- F8 — Validator Rewards: Distributed servers (Validator Nodes) earn a tiny fee for computational power used to secure the network.
- Agent cash-out portal (Requires real-world BDT flow integration).
- USSD / SMS interface for feature phones.
- Social key recovery / Shamir’s Secret Sharing.
- Interoperability with bKash, Nagad, and traditional banks.
The system utilizes a four-layer stack where the blockchain serves as the single source of truth.
- Layer 1 — User App: (React + Vite + Tailwind) Handles JWT/HTTP requests for users (sending/DAO) and agents (cash-in).
- Layer 2 — API Gateway: (Node.js) Traffic director with fast-failure logic. Includes a Health Monitor to blacklist unresponsive validator nodes.
- Layer 3 — Validators: (Node.js + BFT Consensus) Independent servers running balance checks, transaction banning votes, and the Friction Lock.
- Layer 4 — Chain / Ledger: (Hardhat / Polygon Edge) Four simultaneous chain copies for redundancy. Hosts
Transfer.sol,DAO.sol,Freeze.sol, andFlagRegistry.sol.
The risk engine operates off-chain (Node.js), generating a risk score that dictates the on-chain friction delay.
| Rule | Trigger | Risk Points | Action |
|---|---|---|---|
| R1 | First-time recipient | +20 pts | 10 sec friction timer |
| R2 | Amount 1,000–5,000 BDT | +25 pts | 30 sec delay + SMS confirm |
| R3 | Amount > 5,000 BDT | +40 pts | 1 min delay + warning modal |
| R4 | Recipient flagged by 3+ users | +45 pts | 2 min delay + red warning |
| R5 | 5+ transfers in 1 hour | +35 pts | 1 min delay + freeze prompt |
| R6 | Total Score > 70 | Escalate | 3 min lock + dual confirm (Hard Cap) |
bangla-coin/
├── bangla-chain/ # Automation scripts to download and run Polygon Edge nodes
├── contracts/ # Hardhat project (Solidity contracts + deploy scripts)
├── api-gateway/ # Port 5000: Central Express API (Risk Engine + FallbackProvider)
├── gateway-admin/ # Port 6001: React UI monitoring the Gateway
├── validator-template/ # Base code for Validator node backend/UI (to be duplicated later)
│ ├── backend/ # Express server listening to EVM events + Voting
│ └── frontend/ # React dashboard for approving/rejecting bans
└── user-app/ # Port 3000: React Web App for end-users
Run these commands first to install Node.js packages:
npm install
cd user-app && npm install
cd api-gateway && npm install
cd gateway-admin && npm install
cd validator-template/frontend && npm install
cd validator-template/backend && npm install
- 10001, 10002, 10003 -> Hardhat RPC Nodes (Managed via bash scripts you will write).
- 5000 -> Main API Gateway (Node.js)
- 6001 -> Main API Gateway Admin UI (React)
- 3001, 3002, 3003 -> Validator Backends 1, 2, and 3 (Node.js)
- 4001, 4002, 4003 -> Validator Admin UIs 1, 2, and 3 (React)
- 3000 -> Bangla Coin User App (React)
.\start-all.ps1
sudo chmod +x ./start-all.sh && ./start-all.sh
user-app:010000000001,010000000002are agent accounts. Account with any other phone number is a regular user account. The default OTP is123456.Validator Node Admin Panel: The handle isadminand password isadmin.
Built for the Friction Hackathon 2026 by Team SUST SONGLAP