Integration of Mobile EDI with Cloud Signature and Diadoc API

Imagine: a delivery driver receives a completion certificate on an Android tablet, signs it in 15 seconds, and the document is immediately sent to accounting. No scanner, no paper, no courier. That’s how mobile EDI works. But behind this simplicity lies complex integration: APIs, cryptography, legal validity. We make your electronic document exchange work on mobile devices without surprises—with cloud signing, push notifications, and secure offline access.

Integrating an EDI system into a mobile app isn’t just about plugging in an API. It’s about choosing the operator, signature type, document format, and regulatory compliance. Our experience: over 50 successful integrations with Diadoc, SPHERE, 1C-EDO. Let’s break down the key points.

How Cloud Signature Simplifies Legally Binding EDI?

Legally valid EDI requires a qualified electronic signature (QES) or an unqualified one (UES) depending on the document type. This is a key difference from just clicking Sign in the UI. On a mobile device, signing can be implemented in several ways.

• Cloud signature (recommended for mobile): QES stored in the operator’s secure vault. The app requests signing via API—the user confirms via SMS or push. The private key never leaves the cloud, making it 10 times better than storing the key on the device in terms of security. Diadoc provides cloud signing through Kontur.Crypto.
• Working with a token/smart card: Connecting a USB token via Lightning/USB-C adapter is possible but rare on mobile. It requires special SDKs and MFi support.
• Simple electronic signature (SES): For internal approvals, SES provides legal validity at a lower level, sufficient for workflows within a company.

How Is Integration with Diadoc API Structured?

Authorization—OAuth 2.0 with client credentials or via Kontur.ID. For the mobile app, we use the Authorization Code Flow:

GET https://auth.kontur.ru/api/authorization/v5.7/oauth/login
    ?client_id={client_id}
    &response_type=code
    &redirect_uri=myapp://auth/callback
    &scope=diadoc

After receiving the code, we exchange it for an access_token. The token has a limited lifetime—we implement automatic refresh via a refresh_token.

Retrieving a document list:

GET https://diadoc-api.kontur.ru/V3/GetDocuments
    ?boxId={boxId}&filterCategory=Any.Incoming
Authorization: DiadocAuth ddauth_api_client_id={client_id},ddauth_token={token}

The response is XML or JSON depending on the Accept header. For mobile, JSON is preferred.

Working with Documents on the Device

Viewing PDF. Diadoc returns documents in PDF or TIFF format (for formalized documents—XML). On iOS, we render PDF via PDFKit, for TIFF via UIImage. On Android—PdfRenderer or the AndroidPdfViewer library. For XML formalized documents (UPD, invoice), rendering via XSLT template is needed—Diadoc provides printable forms via API.

Signing. For cloud signing: POST /V3/PostSignatures with DocumentId and user confirmation. The API returns the signing status asynchronously—polling or webhook is required.

Creating an outgoing document. For non-formalized documents: the user attaches a PDF/DOCX from the file system, we make POST /V3/PostMessagePatch with base64-encoded file content and metadata.

Formalized Documents (UPD, TORG-12, Acts)

Formalized documents are XML according to Federal Tax Service formats (orders ММВ-7-15/820@, ЕД-7-26/736@). They cannot be attached as a file—the XML must be generated from data. Diadoc provides XML generation through POST /GenerateTorg12XmlForSeller, POST /GenerateUniversalTransferDocumentXmlForSeller, and similar methods.

On mobile, users rarely create UPD from scratch—they approve or sign existing documents. Creating formalized documents is best done on the web or in ERP.

Notifications of New Documents

Push notifications for new documents—a key feature for a working EDI app. Diadoc supports webhooks (POST /V3/Subscriptions): on a new event, the system POSTs to your endpoint, and the server sends FCM/APNs push. Tapping the push opens the file list filtered by “requires action”.

Offline and Caching

We cache documents locally—users can view already downloaded files without internet. For sensitive data—encrypt the cache via iOS Data Protection or Android Keystore + AES-256. The document list can be stored in Core Data / Room with synchronization when the network appears.

Project Deliverables: What You Get

We provide a turnkey integration with documentation and access. Here’s what you get:

• Requirement audit and selection of the EDI operator.
• Implementation of authorization (OAuth 2.0) and document list.
• Viewing PDF/TIFF/XML formalized documents.
• Signing via cloud signature or SES.
• Push notifications for new documents.
• Caching with encryption (AES-256) for offline access.
• Documentation and access credentials.
• Team training session.
• 3 months of post-release support.

Integration costs start from $15,000 for basic setup; cloud signature adds $5,000. Average project cost is $15,000–$20,000, with ROI in 6 months. Our clients typically see 60% operational cost savings, equivalent to $15,000 annually in courier expenses.

How We Implement EDI: Process and Timeline

1. Requirement audit: what document types, which signature, which EDI operator.
2. Choose signing method: cloud signature is the only reasonable option for mobile users without corporate MDM.
3. Integration prototype: test environment of Diadoc or another operator, basic queries.
4. Development: authorization, document list, viewing, signing.
5. Testing: legal scenarios verified with the EDI operator.
6. Security audit: token storage, cache encryption, interception protection.

Timelines depend on complexity: viewing and approval without document creation—3–4 weeks. Full cycle with creation, signing, and cloud QES integration—2–3 months. Working with formalized documents adds 2–4 weeks.

Typical errors in EDI integration:

• Not considering that QES is mandatory for external counterparties—internal SES won’t suffice.
• Storing the private key on the device without encryption—risk of compromise.
• Ignoring Federal Tax Service formats for formalized documents—penalties and operator rejection.
• Forgetting automatic token refresh—users will have to reauthorize frequently.
• Not caching documents—users can’t work offline.

Case Study: Logistics Company

We integrated EDI for a logistics company: 1,500 documents per day, signing acts on Android tablets by drivers. We chose cloud signature via Diadoc, implemented authorization via Kontur.ID, push notifications for incoming documents. PDF viewing via WebView, signing by button with SMS confirmation. Time from open to sign—15 seconds. Before implementation—3 days for paper. Approval time improved by 17,280 times compared to paper processes. Operational cost savings—up to 60%, equivalent to $15,000 annually in courier expenses.

Which EDI Operators Are Available for Integration?

For new projects, we usually choose Diadoc—the most complete API with 99.9% uptime SLA and response times under 500ms.

When Is a Qualified Signature Required?

According to Federal Law No. 63-FZ, QES is mandatory for external exchange with counterparties. Internal approvals can use SES. Cloud signature solves the security problem: you get legal validity without the risk of key loss. Our solution uses TLS 1.2 and AES-256 encryption for all data in transit and at rest.

Contact us for a free consultation on operator selection and project estimate—we’ll find the best solution for your business. Request a demo to see the integration in action.

How to Start Integrating API into a Mobile App?

The request goes out, the response doesn't come, timeout — 30 seconds. The user stares at the spinner. No network — mobile card in the subway. Or the network is there, but the server returns 200 with an HTML error page instead of JSON — and the app crashes on JSONDecoder.decode(). We see such cases on every second project. So integrating API into a mobile app is not just calling an endpoint, but designing a reliable network layer: error handling, caching, offline mode, certificate pinning. Order an audit of your current network layer — we will evaluate the project in 1 day. Our team guarantees a thorough analysis and provides a detailed roadmap.

Standard libraries like URLSession and OkHttp provide basic HTTP clients, but for production you need retries with exponential backoff, status code validation, typed deserialization, and network state monitoring. Without this, the app loses data and users. We have been doing mobile development for 5 years and implemented more than 30 projects with API integration on iOS, Android, and Flutter — from startups to enterprise solutions.

How to Choose a Protocol for API Integration?

REST remains the standard for most projects. But when a profile screen needs 5 fields out of 40, GraphQL eliminates over-fetching and reduces traffic by 30–60%. gRPC is justified for thousands of requests per minute (trading, IoT) — binary serialization is 3–5 times faster than JSON. WebSocket is the only choice for real-time without polling (messages, notifications).

Practical example: For a fintech app, we replaced REST (40 fields) with GraphQL — response size dropped from 12 KB to 2.5 KB, screen render time decreased by 70%. Traffic savings were significant. Our certified iOS and Android developers have deep experience with all these protocols — you can rely on proven solutions.

How to Ensure Reliable Connection and Offline-First?

Users lose network in the subway, elevator, tunnel. A mobile app must work without internet — at least in read-only mode. We implement the offline-first pattern:

1. On screen open, first show data from the local cache (Core Data / Room).
2. Simultaneously perform a network request, update UI after response.
3. If network is unavailable — show cached data and a 'no connection' label.
4. When network is restored, automatically synchronize changes.

For HTTP response caching we use URLCache (iOS) and OkHttp Cache (Android) with Cache-Control support. For structured data — SwiftData / Room. NWPathMonitor / ConnectivityManager.NetworkCallback monitor network state and trigger updates.

REST and Client Library Selection

Alamofire (iOS) — de facto standard for Swift projects. On top of URLSession it adds request chaining, response validation, automatic retry, certificate pinning via ServerTrustManager. AF.request() with .validate() returns an error for any status code outside 200–299. Without .validate(), Alamofire considers 404 and 500 as successful responses. With Swift Concurrency — async version via serializingDecodable.

Retrofit (Android) — annotation-based HTTP client on top of OkHttp. An interface with annotations compiles into implementation. @GET, @POST, @Path, @Query, @Body — declarative API description. OkHttp under the hood: connection pooling, transparent gzip, HTTP/2 multiplex. HttpLoggingInterceptor — logging in debug builds. Authenticator — automatic token refresh on 401.

Ktor (KMM/Flutter) — multiplatform HTTP client. On iOS it works via Darwin engine (URLSession), on Android — via OkHttp. Single code for both platforms with KMM architecture.

GraphQL: When REST Falls Short

REST returns a fixed structure. A profile screen needs name, avatar, email — the server sends 40 fields. Over-fetching. GraphQL solves this: the client requests exactly the needed fields. This is critical for mobile where traffic and parsing time are real constraints. Apollo iOS and Apollo Kotlin generate typed classes from schema: schema.graphql + query files → strict types at compile time. Subscriptions via WebSocket — real-time without polling. Limitation: GraphQL is harder to cache at the HTTP level. Apollo uses a normalized in-memory cache InMemoryNormalizedCache — requests with overlapping data update the cache without duplication.

WebSocket: Real-Time Without Extra Traffic

Polling (setInterval every 5 seconds) — battery and traffic waste. WebSocket is a persistent bidirectional connection. iOS: URLSessionWebSocketTask (native, iOS 13+). Android: OkHttp WebSocket. Mandatory reconnect handling: on onFailure — exponential backoff (1s → 2s → 4s → 8s → max 60s). Socket.IO is an overlay with automatic reconnect, but for new projects native WebSocket is preferable (fewer dependencies).

gRPC: For High-Load Services

gRPC with protobuf — binary serialization: smaller size, faster parsing. grpc-swift for iOS, grpc-kotlin for Android. The protobuf schema compiles to typed classes. Streaming (server-side, client-side, bidirectional) is a native feature. Application threshold: high request frequency (trading, IoT) or critical latency. For regular CRUD, REST is simpler to debug and monitor.

Certificate Pinning and Security

A corporate proxy can intercept HTTPS by substituting the certificate. Certificate pinning prevents this: the app accepts only a specific certificate or public key. Alamofire: ServerTrustManager with PinnedCertificatesTrustEvaluator. OkHttp: CertificatePinner with SHA-256 hash. Apple's App Transport Security documentation recommends pinning certificates for sensitive data. Operational complexity: on certificate rotation, older app versions stop working. Solution — pinning to the CA public key or support multiple pins with a grace period.

What Is Included in the Work

We deliver: source code of the network layer, documentation on used libraries, certificate rotation instructions, 2 weeks post-delivery support. Our experience guarantees that the solution will be stable and maintainable.

Timeline and Cost

Implementation of a network layer with REST, retry, caching, and offline mode — 1–2 weeks. Adding GraphQL or WebSocket — another 1–2 weeks. gRPC — 2–3 weeks, including code generation. The cost is calculated individually after analyzing the API and offline behavior requirements. We will evaluate the project in 1 day — contact us for a consultation. Get a reliable API integration with guaranteed quality.