Sudan’s first offline NFC digital wallet. PoC validated and MVP delivered in five months.

The Challenge

The client faced two distinct but related challenges at the same time. The first was capacity: the core payment platform was experiencing growing demand, with thousands of users depending on it daily, but the company’s in-house engineering team was too small to simultaneously maintain the existing system and build new capabilities at the pace the business required. The second challenge was structural and specific to the local infrastructure environment. Offline NFC payments are technically demanding in ways that online payment systems are not. When a transaction occurs without an internet connection, the wallet balance must be updated atomically on the smart card itself, as the card is the ledger, not a remote server. This means the update must be cryptographically secure, tamper-resistant, and resilient to card removal or device failure mid-transaction. Any weakness in this layer creates a real exposure: balances that can be manipulated, replayed, or duplicated. The hardware dimension added further constraints. The target smart card format, a security-focused NFC card standard, has its own authentication protocol and cryptographic requirements. Building a reliable Android integration required deep knowledge of the card’s command set and a disciplined approach to key management and session handling. The Android Keystore had to be used correctly to protect cryptographic material on the terminal device. None of this is off-the-shelf. The enterprise also needed a backend for user management, transaction records, and a periodic sync mechanism to reconcile offline transactions against a central ledger when connectivity became available. Both tracks needed to advance at once, within a five-month window, without disrupting existing service.

The Approach

Gradion deployed on two parallel tracks from the start of the engagement. The first track was embedded engineering support. A dedicated engineer was placed directly within the client’s in-house team, contributing to day-to-day platform development and enhancement. This arrangement gave the company immediate additional engineering capacity without the overhead of a traditional hiring process, and it improved team velocity on the existing payment system while the innovation work proceeded in parallel. The second track was the NFC offline payment initiative. The embedded model was chosen deliberately: The client’s team needed to own the platform after delivery, and working alongside Gradion engineers transferred both code and knowledge. The core technical deliverable was a secure NFC-based Android proof of concept enabling offline smart card transactions using a security-focused NFC card standard. Android Keystore was used to manage cryptographic keys on the terminal device, with atomic balance updates written to the card at the point of transaction, ensuring that every offline payment was either fully committed or cleanly rolled back, with no partial state. This design prevents balance manipulation and ensures card integrity across intermittent connectivity cycles. Following successful validation of the proof of concept, Gradion extended the work into a full MVP. The backend covered user accounts, transaction records, and a periodic sync architecture that reconciled card-based offline transactions against the central ledger whenever connectivity was available. Offline-capable Android terminals were built to sync automatically when internet access resumed, with no manual intervention required from the merchant or user. The full scope, including the NFC PoC, transaction backend, and offline-capable Android terminals, was delivered within the five-month target, with a lean team: one senior Android engineer and a tech lead at 10% allocation.