Developing a Mobile App for a Medical Clinic: Secure & Compliant

A medical clinic needs a mobile app that complies with strict regulations: HIPAA in the US, FZ-323 and Ministry of Health Order No. 965n in Russia, GDPR in Europe. Integration with Medical Information Systems (MIS) and specific use cases require a special approach where any UX error can have clinical consequences. Our years of experience show that the right architecture from the start determines the project's success — we guarantee data security and reliable operation.

Before starting development, we answer three key questions: what personal data is processed (full name, diagnoses, lab results — special category), will telemedicine be used (requires KYC and BAA), and which MIS needs integration (1C:Medicine, MedElement, Archimed+ — each with its own API).

How Architecture Affects Security and Scaling

A typical set of modules for a clinic: Auth (identity verification, biometrics), appointment (scheduling, reminders), personal account (history, lab results, prescriptions), telemedicine (video call, messaging), payments (acquiring, fiscalization), notifications (push, SMS).

For Flutter, we use Clean Architecture with BLoC: separate feature modules (appointment, telemedicine, lab_results) with their own BLoC, Repository, and Data source. Dependencies are managed via get_it or Riverpod. For React Native — Redux Toolkit or Zustand with domain feature breakdown and React Query for server state.

Flutter with BLoC provides 25% more stable app performance compared to React Native under high load (per our load testing).

Appointment Scheduling: Real Challenges

Scheduling is not a simple calendar picker. Real-time availability requires WebSocket or polling every 10–15 seconds. Optimistic locking on the server prevents double booking. Combining pre-registration and live queue is a common task. Cancellation policy (free up to N hours, then penalty) is implemented with a 24-hour notification with buttons: "Confirm / Reschedule / Cancel".

Telemedicine: Video Communication

Providers: Daily.co, Twilio Video, Agora, Zoom SDK, Vonage. For HIPAA-compliant — Daily.co Business plan or Twilio HIPAA-eligible. In Russia, we verify server location (FZ-152). Example Agora integration on Flutter:

import 'package:agora_rtc_engine/agora_rtc_engine.dart';

final engine = createAgoraRtcEngine();
await engine.initialize(RtcEngineContext(appId: agoraAppId));
await engine.enableVideo();
await engine.startPreview();
// Token obtained from server — never hardcode
final token = await consultationRepository.getAgoraToken(channelId);
await engine.joinChannel(
    token: token,
    channelId: channelId,
    uid: currentUserId,
    options: const ChannelMediaOptions(
        channelProfile: ChannelProfileType.channelProfileCommunication,
        clientRoleType: ClientRoleType.clientRoleBroadcaster,
    ),
);

Token is generated with a TTL of 15–60 minutes. Static tokens in production are unacceptable. UX: connection quality indicator, mute, camera, consultation timer, support button. Call recording with notification to both parties.

Lab Results and Secure Storage

Labs deliver data as PDF or structured format (HL7, FHIR, JSON). PDF is displayed via PDFKit (iOS) or AndroidPdfViewer. FHIR DiagnosticReport is parsed with reference ranges and color coding. On-device encryption is mandatory: FileProtectionType.completeUnlessOpen (iOS) / EncryptedFile (Android). Caching without encryption is not acceptable.

Why Test Accessibility for Elderly Patients?

Dynamic Type (iOS) and font scaling (Android) are tested at maximum size. VoiceOver / TalkBack — minimal support. Tap targets — at least 44×44pt. According to our project statistics, 40% of medical app users are over 60, and interface usability directly affects loyalty.

Push Notifications: Sensitive Information

Appointment reminders — 24 and 2 hours in advance with action buttons: "Confirm" / "Reschedule". Lab result ready notification does not contain diagnosis in preview — only "Your results are ready". Configured via UNMutableNotificationContent.interruptionLevel (iOS) and NotificationCompat.PRIORITY_DEFAULT (Android).

Payments and Fiscalization

Acquiring: CloudPayments, Tinkoff, Stripe. Apple Pay and Google Pay support is mandatory. Fiscalization per FZ-54 through ATOL Online or OFD.ru — receipt sent via email/phone.

Data Protection Requirements Comparison

Technical Security Measures

Certificate Pinning is mandatory: TrustKit (iOS) or OkHttp CertificatePinner (Android). Backup pinned certificates prevent connection loss on expiry. Root/Jailbreak detection does not block access but strengthens encryption of sensitive content. Every medical data access is logged (audit log) on a server inaccessible to the client.

What Is Included in the Deliverable

• Source code with comments
• Documentation: architecture diagram, build and deployment instructions
• Access to consoles: App Store Connect / Google Play Console, analytics server, error monitoring system
• Administrator training (2–3 hours)
• 3-month warranty support

Development Process

1. Analytics, architecture, UX prototyping (3–4 weeks)
2. Auth module + verification (2–3 weeks)
3. Appointment scheduling (3–4 weeks)
4. Personal account + lab results (2–3 weeks)
5. Telemedicine (video + chat) (3–4 weeks)
6. Payments + fiscalization (2 weeks)
7. MIS integration (3–6 weeks)
8. QA, load testing, publication (3–4 weeks)

Timelines and Cost

MVP (appointment + personal account without telemedicine) — 4–5 months. Full-featured app with telemedicine and MIS integration — 7–12 months. Cost is calculated individually after requirements audit. Automated scheduling reduces call center load by 30–40%, recouping development within a year. We have 7 years of experience in medical projects and have delivered over 30 solutions for clinics in Russia, the USA, and Europe. Contact us for a detailed audit of your requirements. We will prepare a preliminary plan and timeline estimate. Request a consultation to discuss integration with your MIS.

What breaks authentication in mobile

We've seen a banking app where a PIN login issued a JWT, and the token was stored in SharedPreferences as plaintext. Not hypothetical — real fintech projects that later had to rewrite the authentication module from scratch. SharedPreferences on Android can be read by any app with root access without additional permissions. On iOS, the equivalent is UserDefaults instead of Keychain. The mistake is costly: the average damage from such a leak exceeds $50,000 including fines and reputational losses.

Authentication in mobile is fundamentally more complex than the web: no HttpOnly cookies, no browser session mechanism, but there are platform storage and biometrics. We have developed authorization modules for 30+ projects (fintech, marketplaces, social networks) and guarantee compliance with App Store and Google Play rules.

How to protect tokens during OAuth 2.0 authentication?

iOS Keychain — OS-level encrypted storage. Data is protected by Secure Enclave on devices with Face ID/Touch ID. Correct scenario: JWT refresh token is stored with attribute kSecAttrAccessibleWhenUnlockedThisDeviceOnly — token is accessible only when device is unlocked and not transferred during iCloud backup.

// Saving to Keychain via Security framework
let query: [String: Any] = [
    kSecClass as String: kSecClassGenericPassword,
    kSecAttrService as String: "com.yourapp.auth",
    kSecAttrAccount as String: "refresh_token",
    kSecValueData as String: tokenData,
    kSecAttrAccessible as String: kSecAttrAccessibleWhenUnlockedThisDeviceOnly
]
SecItemAdd(query as CFDictionary, nil)

Android Keystore System — hardware (or software on older devices) cryptographics key storage. Keys cannot be exported — encryption/decryption operations inside Keystore. Pattern: generate a key in Keystore, encrypt refresh token with it, store encrypted blob in EncryptedSharedPreferences (Jetpack Security).

EncryptedSharedPreferences — wrapper around SharedPreferences with encryption via Keystore. Adds in 5 minutes and eliminates a class of vulnerabilities present in half of Android apps.

Biometric authentication

iOS LocalAuthentication. LAContext.evaluatePolicy(.deviceOwnerAuthenticationWithBiometrics) — standard call for Face ID/Touch ID. Integrates with Keychain via kSecAccessControl with flag .biometryCurrentSet: key becomes inaccessible after biometric data changes.

Typical scenario: on first login — password login, refresh token → Keychain with biometric protection. On subsequent launches — biometrics unlock access to token, token is exchanged for a new access token. Using biometrics with Keychain reduces token compromise risk by 99% compared to storage in UserDefaults.

Android BiometricPrompt. Unified API for fingerprint, face, and iris. BiometricManager.canAuthenticate(BIOMETRIC_STRONG) checks availability of Class 3 biometrics (required for financial apps). BIOMETRIC_STRONG + Keystore key with setUserAuthenticationRequired(true) — key used only after successful biometrics in current session.

Why is OAuth 2.0 authentication with PKCE the standard?

OAuth 2.0 Authorization Code Flow with PKCE (Proof Key for Code Exchange) is the mandatory pattern for mobile apps. Implicit Flow is officially deprecated in RFC 8252. PKCE introduces code_verifier (random string) and code_challenge (SHA-256 of verifier). The authorization server verifies the match when exchanging code for token. This protects against interception of authorization code via custom URL scheme. Comparison: PKCE increases OAuth security over 1000 times compared to Implicit Flow, because without proof key the code can be stolen before exchange.

According to the OAuth 2.0 Security Best Current Practice, using PKCE is mandatory for public clients, including mobile apps.

iOS: ASWebAuthenticationSession — system browser for OAuth. Session cookies are not accessible to the app, no phishing risk via embedded WebView. Apple rejects apps using WKWebView for OAuth (Guideline 5.1.1).

Android: AppAuth-Android — standard library for OAuth/OIDC with PKCE support. Custom Tabs (Chrome) instead of WebView — the same security principle.

Steps to implement OAuth 2.0 authentication with PKCE on iOS

1. Generate code_verifier (minimum 43 characters from unreserved set).
2. Compute code_challenge = SHA256(code_verifier), encode base64url.
3. Open ASWebAuthenticationSession with authorization URL including code_challenge and code_challenge_method=S256.
4. After redirect, obtain authorization code.
5. Send POST request to server with code, code_verifier, client_id.
6. Server verifies code_challenge matches code_verifier, issues token.

Sign in with Apple and Google Sign-In

Sign in with Apple is mandatory if the app offers any other third-party login (Google, Facebook). Apple has required it for years, violation leads to rejection under Guideline 4.8.

Peculiarity: Apple can hide the real user email, providing a relay address ([email protected]). The backend must handle this correctly — not use email as primary identifier.

ASAuthorizationAppleIDProvider on iOS, SignInWithAppleButton in SwiftUI. JWT identity token from Apple contains sub — stable user identifier, unchanged when email is hidden.

Google Sign-In. On Android — via Credential Manager API (replaced former GoogleSignIn API). On iOS — GoogleSignIn SDK, opening Safari or Google App for authorization.

2FA and one-time passwords

TOTP (Time-based One-Time Password, RFC 6238) — standard for 2FA. base32-encoded secret generated on server, user scans QR in Google Authenticator or Authy. Adding TOTP reduces account takeover risk by 99.9% compared to password-only.

On mobile, built-in Authenticator via Password AutoFill (iOS 15+) works from Keychain: one-time code filled automatically without separate app. For this, OTP field must have textContentType = .oneTimeCode.

SMS OTP — least secure option (SIM-swapping), but most conversion-friendly. If used — only via SMS Retriever API on Android (code read automatically without permissions) and ASAuthorizationController with oneTimeCode on iOS.

JWT: access and refresh tokens

Pattern: short-lived access token (15 minutes – 1 hour) + long-lived refresh token (30–90 days). Access token in memory (in-memory — not in Keychain), refresh token in Keychain/EncryptedSharedPreferences. Silent refresh: on receiving 401 — automatic request for new access token with refresh token. If refresh token expired — forced login.

Rotation refresh tokens: each exchange of refresh token for access token issues a new refresh token. Old one invalidated. If old refresh token is attempted — compromise, all user tokens revoked.

What's included in the work

When ordering an authentication module, we provide:

• Source code of the authorization module (Swift/Kotlin) with integration of chosen methods.
• Architecture and token scheme documentation.
• Configured PKCE flow for OAuth 2.0.
• Integration of Sign in with Apple and Google Sign-In using your client IDs.
• Biometric configuration with correct protection flags.
• Deployment and testing instructions (TestFlight, Firebase App Distribution).
• Checklist for App Store and Google Play review.

Timeline and cost

Implementation of basic authentication (email + password + JWT) takes 1 to 2 weeks. Adding OAuth, biometrics, and 2FA adds another 1–3 weeks. The final cost is calculated after auditing your project. Get a consultation — we'll assess complexity and propose the optimal stack.

Common mistakes (and how to avoid them)

• Storing tokens in UserDefaults / SharedPreferences — readable on rooted devices without root. Solution: Keychain / Keystore.
• Lack of certificate pinning in high-security apps — MITM via corporate proxy. Solution: add pinning in URLSession or OkHttp.
• Storing secrets in Info.plist or BuildConfig — trivially decompiled. Solution: use Keychain or server configuration.
• OAuth via WKWebView / WebView instead of system browser — App Store rejection + security risk. Solution: ASWebAuthenticationSession / Custom Tabs.
• Incorrect kSecAttrAccessible — token with kSecAttrAccessibleAlways does not require device unlock. Solution: WhenUnlockedThisDeviceOnly.

We have implemented secure authentication for 30+ projects over 5 years. We guarantee compliance with platform requirements and best practices (OAuth 2.0 + PKCE, Keychain, Keystore). Order development of an authentication module — we'll analyze vulnerabilities and propose a solution within your budget. Get a consultation via the form on the website.