A wallet app with the keys encrypted
and the compliance questions asked early
A wallet app is the one category where a shipped-looking demo and a production-ready system are worlds apart: seed phrases, key encryption and swap aggregation either hold up under real money or they do not. We have built one across ten chains, and the lesson that matters most is that the compliance and custody question gets answered before the first screen, not after.
What it is and who needs it
A fintech or wallet app lets a user hold, send, receive and often swap value, crypto assets, fiat balances or both, from their phone, with the key management and security architecture that a mistake here is far more costly than in almost any other app category. It is for a crypto product building its own wallet instead of embedding a third-party SDK, a fintech startup building a mobile-first balance and payments product, or a brand adding a wallet feature to an existing app.
The custody question comes first, always: a fully non-custodial wallet, where the user’s keys never leave their device unencrypted and we never touch funds, is a fundamentally different and generally simpler build than one requiring regulated custody through a licensed partner. We settle this with you before any architecture decision, because it changes nearly everything downstream.
What is inside
Keys are generated as HD wallets (BIP39/BIP44) from one seed phrase and extended across however many chains your product needs, Ethereum and its compatible chains, Solana, Bitcoin, TON and others, so a user manages one seed instead of ten. Seeds are encrypted at rest with AES-256-GCM, never stored or transmitted in a recoverable plain form, and account actions are protected by TOTP 2FA with argon2id password hashing, the same standard we apply to every build that touches sensitive credentials.
Live balances and prices update over WebSocket rather than slow polling, and where swaps are in scope, we integrate aggregators like 1inch for EVM chains and Jupiter for Solana so users get competitive rates without the product running its own exchange. If a licensed custody or card partner is part of the roadmap, we structure the backend so that integration is additive, not a rebuild.
We also build in the operational detail that matters once a wallet is live with real users: rate limiting on sensitive endpoints so a credential-stuffing attempt cannot brute-force its way past 2FA, a recovery flow for a lost device that does not create a backdoor an attacker could exploit, and transaction simulation before a user signs anything irreversible, so a mistyped address or an unexpected fee is caught before funds move, not after a support ticket arrives. Every build gets a dedicated incident-response plan documented before launch, because a wallet is the one product category where “we will figure it out if something goes wrong” is not an acceptable answer.
How we build it
- Settle custody first. Non-custodial by default; a licensed partner only where the product genuinely requires it, decided before architecture, not after.
- Design key management to the standard, not around it. Encryption at rest, 2FA, and hashing choices follow established cryptographic practice, not a shortcut taken to save a sprint.
- Isolate chain-specific logic. A monorepo structure keeps Ethereum, Solana, Bitcoin and TON logic separate, so a bug in one chain’s integration cannot silently affect another.
- Security review before real funds touch it. A dedicated review pass on key handling and transaction signing before any build goes near production value.
- Launch with audit logging. Every account and transaction action is logged, so a dispute or incident has a real trail.
Timeline and price
| Tier | Price | What’s included | Timeline |
|---|---|---|---|
| MVP | from $12,000 | Non-custodial wallet, two to three chains, encrypted keys, 2FA | 10 to 16 weeks |
| Production | from $20,000 | MVP plus full multi-chain support, live pricing, swap aggregation | 16 to 22 weeks |
| Full control, handover-ready | from $34,000 | Everything in Production plus full security documentation and handover for your own engineering team | 16 to 22 weeks |
What you own at the end
The full repository, the key-management architecture, and the backend, deployed on infrastructure in your name. Documentation covers the encryption design, the chain integrations and the audit logging, so a security review by your own team or an outside auditor has something real to evaluate, not a black box.
Related
See the development service page for our general build and security approach, and the marketplace mobile app page for adjacent product-with-money builds. For infrastructure, see crypto wallet integration and pci-aware payment architecture. For the real build behind these numbers, see the multichain crypto wallet across ten networks.
Building a wallet or fintech product and need the custody question answered honestly before you commit to an architecture? Get in touch and we will walk through it with you.
FAQ
How much does a crypto wallet or fintech app cost?
From $12,000 for a non-custodial wallet across two to three chains with encrypted key storage and 2FA. Multi-chain support across ten networks, swap aggregation and a card-ready backend structure typically runs $18,000 to $28,000.
Do you handle custody of user funds?
By default we build non-custodial, meaning the user's keys never leave their device unencrypted and we never hold funds. If your product needs custodial features, that requires a licensed partner for regulated custody, and we build the integration layer to that partner rather than acting as the custodian ourselves.
What stack do you use for a wallet app?
React Native and Expo or a native client, a Fastify or FastAPI backend, PostgreSQL and Redis, and chain-specific libraries like viem for Ethereum-compatible chains, @solana/web3.js for Solana, bitcoinjs-lib for Bitcoin, and @ton/ton for TON, all in a monorepo structure that keeps chain logic isolated.
Who owns the code and the architecture?
You. The repository, the encryption and key-management design, and the backend are yours from the first commit, deployed on infrastructure in your name. Nothing about running the wallet depends on us continuing the relationship.
What about regulatory compliance?
We are not a law firm and do not give regulatory advice. We build to security best practices (encryption at rest, 2FA, audit logging) and structure the system so a licensed partner or compliance counsel can plug into it, but the licensing and compliance decisions are yours to make with qualified counsel.