Flutter Crypto App for iOS, Android, Web & Desktop
A Flutter fintech app that turns crypto and gift cards into Naira in a lender's own bank account: generate a deposit address, watch the rate, sell, and withdraw, with identity and bank verification wired in.
01 / The Challenge
Money leaves the app and has to land in the right account
QuickChain's users are Nigerian traders, freelancers and businesses converting crypto into spendable Naira. Every step in that flow is a place where real money goes missing: a mistyped deposit address, a bank account number that belongs to someone else, an unverified identity behind a payout, or a rate that moved between reading it and selling. The app had to make each of those steps hard to get wrong, on the mid-range Android devices most of the market actually carries.
Crypto deposit addresses are unforgiving, one transposed character and the funds are gone with no recovery path
Payouts go to Nigerian bank accounts, so an account number had to be verified as belonging to the user before any money moved
Regulated cash-out means identity verification, but a heavy in-app KYC SDK is exactly where first-time users abandon
Rates move constantly, so users needed live charts and alerts rather than a number that silently goes stale
A fintech backend ships features faster than app-store review allows, so the app could not hard-code its own navigation
02 / Here is What We Did
A thin, typed client layer under a provider-per-screen UI
We built QuickChain in Flutter with Provider, pairing every page with its own provider so state stays local to the screen that owns it, and routing through go_router. Underneath sits a hand-rolled HTTP layer, a builder-style Request, a header builder and a request executor returning a typed Success/Failure result, so no screen ever touches a raw response, and ten repositories, one per domain, are the only things that know an API exists.
Navigation is server-driven: a menu-visibility endpoint keyed by platform and app version decides which modules a given build shows, so features can be switched on without a release.
Account, Captcha & Verification
Built sign-up, sign-in and password recovery gated by a server-issued image captcha, with device fingerprinting on login, optional biometric unlock, and a KYC flow where the Veriff session is created server-side and the app surfaces start, pending, verified and failed states.
Sell Crypto & Gift Cards
Wired the sell flow into the client's crypto infrastructure: per-asset deposit addresses rendered as scannable QR with copy-to-clipboard, live price charts, rate alerts, and on-chain transaction history, alongside a gift-card flow that uploads card photos for valuation.
Wallet, Payouts & Release Control
Added the Naira wallet with separate cashback and referral balances, bank-account verification before payout, withdrawal with history, push notifications, and a forced-update gate plus server-driven menu visibility to control what each build exposes.
03 / Features
Everything between a wallet address and a bank account
Per-asset deposit addresses generated on demand and rendered as a scannable QR code with copy-to-clipboard, removing the hand-typed address as a failure mode entirely.
Live price charts per coin backed by a rate endpoint, plus a rate-alert feature that notifies a user when their target price is hit rather than making them watch the screen.
Gift-card selling as a second cash-out path, browse the supported card list, submit card photos through a multipart upload, and track the valuation alongside crypto transactions.
A Naira wallet split into main, cashback and referral balances, each with its own balance call and withdrawal history, so users can see where earned money came from.
Bank-account verification before any payout, the account number is checked against the bank's records so a withdrawal cannot be sent to a mistyped or third-party account.
Identity verification through Veriff with the session created server-side, keeping the heavyweight verification flow out of the app binary while the app tracks and reflects its status.
Server-issued image captcha on sign-up, sign-in and password reset, combined with device fingerprinting at login as a second signal on every session.
A forced in-app update gate driven by an app-version endpoint, plus biometric unlock, offline detection and push notifications through Firebase Messaging.
04 / Technologies
Flutter with a hand-built client layer over a fintech backend
05 / Results & Impact
A production fintech app on both stores
“The fastest, cleanest, and most reliable way to convert crypto to cash in West Africa, built with global infrastructure standards.”
QuickChain, Quchange Technologies
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