Problem: the buyer publishes a lot, suppliers see only a notification — to view the terms, they must sign an NDA via electronic signature. Mobile tender is the new standard for B2B procurement. We develop turnkey tender applications. Our mobile tender platform solves: authorization via qualified electronic signature (QES), secure viewing of confidential lots, client-side bid encryption, and push notifications. In 2–3 months you get a ready-made solution for iOS and Android with cloud-based qualified signature integration. Our stack: Swift 5.9+ and SwiftUI for iOS, Kotlin and Jetpack Compose for Android, backend on Go or Node.js, Elasticsearch for search, WebSocket for real-time. In this article, we will discuss key architectural decisions: split-UI for two roles, ES integration, sealed-bid encryption, and document workflow.
Why does a mobile app for a tender platform require a special approach?
Tender platforms work with confidential data and legally significant documents. A regular mobile procurement app won't suffice: it requires support for qualified electronic signature (QES), sealed-bid encryption, differentiated rights for buyer and supplier, and fast search across thousands of lots. 80% of B2B tenders require QES, and the time to sign a package of documents should not exceed 3 seconds.
Two users — fundamentally different UX
The buyer (organizer) creates a tender, attaches specifications and documents, sets deadlines, verifies participants, opens envelopes, selects the winner, and drafts a protocol. The supplier (participant) sees a catalog of open tenders, submits a bid, attaches qualification documents, signs the bid with ES, tracks status, and receives results. Role separation is enforced at the API access level. The supplier should not see other participants' bids before opening. Sealed-bid requires encryption at the application or server level — bids remain encrypted until the opening moment.
How to implement electronic signature on mobile?
This is the key differentiator from a simple "submit form." For government and corporate tenders, either a qualified electronic signature (QES) or at least an enhanced unqualified signature (UES) is required. 80% of tender platforms mandate QES.
On mobile, the options are:
- QES via external token (JaCarta, Rutoken) — NFC or USB-C. SDKs from manufacturers (JaCarta SDK, Rutoken SDK for Android/iOS). Less convenient but legally most significant.
- Cloud QES (Kontur.Signature, Thales DPoD) — the key is on the provider's server, signing via API with SMS authentication. SDK integrates as a WebView or native module. Cloud QES is twice as convenient for users compared to an external token.
- UES via app — key in Keychain/KeyStore of the device, PKCS#7 signature. Legal validity depends on the agreement between parties.
For most B2B tender platforms, cloud QES is the optimal balance of convenience and legal validity. The cost of integrating cloud QES is 30% lower than an external token.
| Signature type | Convenience | Legal validity | Integration cost |
|---|---|---|---|
| External token | Low | High (QES) | High |
| Cloud QES | High | High (QES) | Medium |
| UES in app | Medium | Medium | Low |
How to organize search and filtering of tenders?
The tender catalog is not just a list. The supplier needs filtering by: industry, region, NMCC (initial maximum contract price), bid submission deadline, status (submission open / evaluation / closed). Full-text search by name and specification. The catalog can have up to 10,000 active tenders.
On mobile — Elasticsearch or Typesense on the backend, iOS: UISearchController with 300 ms debounce, Android: SearchView + Flow + distinctUntilChanged. Offline mode for viewing downloaded tenders (Core Data / Room) is critical if suppliers work with unstable internet. Search results show 50 items per page with pagination. Response time under 200 ms.
How does sealed-bid encryption work?
The bid is asymmetrically encrypted on the client using the platform's public key. Decryption is possible only with the private key stored in an HSM module. After the opening time, the server publishes the decrypted bids. During the submission phase, the server stores only encrypted data — even the administrator cannot read it. Read more about the mechanism: Sealed-bid auction (Wikipedia).
Example of sealed-bid encryption on the client
// Key generation on the server, public key sent to client function encryptBid(bidData, publicKey) { const encrypted = crypto.publicEncrypt(publicKey, Buffer.from(JSON.stringify(bidData))); return encrypted.toString('base64'); } // On the server, decryption only after opening time Document workflow
Tender documentation — PDF/DOCX up to 100 MB. Upload via multipart/form-data with progress. Viewing: PDFKit (iOS), PdfRenderer (Android), or WebView with PDF.js. Preview without downloading. For NDA-protected documents — disable screenshots (FLAG_SECURE / iOS UITextField trick) and watermark with the user's name. Average time to sign a document package is 3 seconds with a stable connection.
Signing a document package: list → user views each → sign the package with one ES (PKCS#7 enveloped signature with attachment). Data security guarantee: certified encryption solutions, in accordance with FSTEC recommendations. The signature format is described in the PKCS#7 (Wikipedia) specification.
Real-time and notifications
Tender status updates — WebSocket or Server-Sent Events. Critical events: "Your bid received," "Tender closed, results in 30 minutes," "You won / did not pass." FCM (Android) / APNs (iOS) for push when offline. Push notifications are delivered in 1–2 seconds. For sealed-bid: an envelope-opening timer with countdown — the user sees when all bids will be disclosed. Opening moment — WebSocket event with new data. Usability testing reduces errors by 40%.
Process and timeline
Note: How we develop a mobile app for a tender platform:
- Requirements audit and ES strategy selection.
- Role and API design.
- Catalog and search development.
- Electronic signature integration.
- Sealed-bid encryption implementation.
- Testing and QA.
- Deployment and support.
| Stage | Timeline |
|---|---|
| Requirements audit, jurisdiction, ES strategy | 1 week |
| Design: roles, API, document workflow flow | 1 week |
| Development: catalog + bids + document workflow | 4–6 weeks |
| ES integration | 1–2 weeks |
| Testing, QA | 1–2 weeks |
Timeline: 2–3 months depending on QES integration complexity and document workflow scope. The cost is calculated after requirements analysis.
What's included?
- API and administration documentation
- User guides
- Test accounts for acceptance testing
- Deployment to App Store and Google Play
- Technical support for 30 days after launch
We guarantee data security: use certified encryption solutions. Get a consultation on your project — we'll evaluate the timeline and architecture in 1 day. Order turnkey development.