CryptoBump - Crypto Payments as Easy as a Handshake

The Problem with Crypto Payments

❌ Complex Addresses

Copying 42-character addresses is error-prone and intimidating for non-technical users.

❌ QR Code Friction

Scanning QR codes in social settings is clunky and breaks the flow of interaction.

❌ High Barriers

Web3 UX is too complex for everyday peer-to-peer transactions like splitting bills or gifting.

How It Works

Create Voucher

Alice locks 0.001 ETH in the smart contract. The app generates a random 32-byte secret and stores only its keccak256 hash on-chain.


                    createVoucher(hash, 0x0, amount, 24h)

Bump Phones

Alice and Bob touch their iPhones. Using Multipeer Connectivity, the secret is transferred peer-to-peer. No servers, no internet needed.


                    MCSession.send(secretBytes)

Redeem Instantly

Bob receives the secret and taps "Redeem". The smart contract verifies keccak256(secret) matches the hash and transfers the ETH to Bob's wallet.


                    redeem(secret) → 0.001 ETH to Bob

Tech Stack

🔷

Base Sepolia L2

Ultra-low gas fees (~$0.001/tx)

📜

Solidity 0.8.28

Smart contract with OpenZeppelin security

🔨

Hardhat 3

Development & deployment framework

🧪

Foundry Testing

14 comprehensive tests (all passing)

📱

Flutter (iOS)

Cross-platform mobile app

🔗

web3dart

Blockchain integration library

📡

Multipeer Connectivity

Apple's P2P proximity framework

🔐

Keccak-256

Cryptographic hash function

✅ Deployed Smart Contract

Production-ready contract on Base Sepolia with comprehensive test coverage

📍 Contract Address 0xA0bbf7730C9065830c51d2A57b2C0A98d3876bD1

🌐 Network Base Sepolia Testnet (84532)

📅 Deployed October 18, 2025

🔍 Explorer View on BaseScan →

🛡️ Security Features

✅ ReentrancyGuard

✅ SafeERC20

✅ CEI Pattern

✅ Custom Errors

✅ 14/14 Tests Passing

How It Works: Complete Flow

👤 Alice (Sender)

🔐 Generates random secret (32 bytes)

🔒 Computes keccak256(secret) = hash

💸 Locks 0.001 ETH in contract

↓

📜 Smart Contract

Base Sepolia L2

Stores: vouchers[hash] = {

creator: Alice

amount: 0.001 ETH

expiry: 24h

}

↓

📱 Bump Transfer

Multipeer Connectivity

Alice touches Bob's iPhone

Secret transferred P2P (encrypted)

No internet needed ✨

↓

👤 Bob (Receiver)

📲 Receives secret on his device

🔓 Calls contract.redeem(secret)

✅ Contract verifies hash matches

💰 Bob receives 0.001 ETH!

🔐 Security Highlights

✅ Secret never stored on-chain (only hash)

✅ One-time use (cannot redeem twice)

✅ Time-locked (24h expiry for refund)

✅ Trustless (no intermediaries)

Send Crypto with a Bump