Logging in feels simple on the surface. But under the hood, session management and API authentication are where things actually break or hold together. If you’re using a mobile app to trade on an exchange like Upbit, you need to think beyond passwords—about tokens, device trust, refresh strategies, and what happens when the network or the user goes sideways.
I’m writing from years of building and auditing crypto apps. I’m biased toward defense-in-depth. That said, some trade-offs are pragmatic: convenience for users matters, too. So here I sketch a practical approach you can use whether you’re a developer building an app, or an advanced user trying to understand how your device talks to the exchange.
Core concepts: sessions vs. tokens vs. API keys
Sessions are logical constructs that mean “this client is currently authenticated.” For mobile apps, sessions typically map to tokens. Server-managed sessions (stateful) keep a server-side record. Tokens (stateless, e.g., JWTs) carry claims and can be verified without server state. API keys are long-lived credentials used for programmatic access. Each has pros and cons.
Use short-lived access tokens for day-to-day requests and refresh tokens to obtain new access tokens. Store refresh tokens securely. Period. If a refresh token leaks, an attacker can mint new access tokens, so treat refresh tokens like primary credentials.
For app users trying to reach the exchange quickly, this page has a practical signpost for authenticating into Upbit: upbit login. It’s a good starting point for getting your account credentials set up, but keep reading for security practices you should expect from any client or third-party app.
Mobile-specific best practices
Mobile brings device-specific features and threats. You have secure enclaves, biometric APIs, and platform key stores. Use them.
Store tokens in the OS-provided secure storage: Android Keystore, iOS Keychain (prefer Secure Enclave when available). Don’t persist tokens in plain local storage or in files. If you must cache something, encrypt it with keys only available to the app and tied to the device—or better, to the user biometric.
Implement biometric re-auth for sensitive actions (withdrawals, API key creation). This reduces the risk posed by a stolen device. Be mindful: biometrics are convenience, not a silver bullet; combine them with short token lifetimes and server-side checks.
OAuth2 + PKCE for mobile clients
OAuth2 with PKCE is the modern pattern for mobile native apps. It prevents interception of authorization codes by using a code challenge and verifier pair. If you control both client and server, PKCE is still worth implementing for consistency and defense-in-depth.
Flow in practice: user signs in via a secure authorization endpoint, the server issues a short-lived access token and a long-lived refresh token, and the client uses PKCE during the initial authorization to bind the code exchange to that client instance. Rotate and revoke refresh tokens on logout or suspicious activity.
API authentication patterns and API key hygiene
For programmatic trading, API keys are common. But long-lived keys are risky. Prefer scoped keys with minimal permissions—read-only vs. trading vs. withdrawals. If your app offers API key management, allow users to set IP restrictions, per-key expirations, and per-key rate limits.
Implement HMAC signing on sensitive endpoints: require the client to sign requests with a secret and timestamp to prevent replay attacks. Validate timestamps server-side with reasonable skew tolerance. Reject old or malformed signatures.
Session expiration, rotation, and revocation
Short-lived access tokens (minutes to an hour) and refresh tokens (days to months) are a sensible default, but the exact numbers depend on your risk tolerance. Rotate refresh tokens on each use (refresh token rotation): when the client exchanges a refresh token for a new access token, issue a new refresh token and invalidate the old one. This thwarts token replay if a stolen refresh token is used.
Support immediate revocation: users need a way to log out everywhere or revoke all API keys. On the server, maintain a revocation list or a token-version field in the user record so that you can invalidate tokens without maintaining full session state if you use JWTs.
Device binding and anomaly detection
Detect unusual device or login behavior: new device fingerprint, new geo location, or sudden high‑frequency order placement. When things look off, require step-up authentication (2FA, additional email/SMS confirmation) before sensitive actions.
Device binding can be useful: associate a token with a device ID or certificate so that a refresh token stolen from backups or synced storage can’t be used from another device without additional proof.
Network security and certificate handling
Always use TLS. Pin certificates for production mobile apps if you can manage updates, or use a robust update strategy that supports pin rotation—improper pinning can brick connectivity, so plan for that.
Prefer standard libraries for TLS, crypto, and HMAC. Reimplementing cryptography is a fast route to subtle bugs.
Edge cases and practical trade-offs
Offline signing: power users or institutional traders might want offline signing of orders for non-custodial setups. That’s different—orders are signed client-side and pushed to an execution engine. If you’re building such flows, separate key management entirely from session tokens.
Performance vs. security: requiring re-auth for every trade is secure but will kill UX. Use session context to allow low-risk operations while gating high-risk ones. Profile user behavior and tune thresholds.
FAQ
How should a mobile app store refresh tokens?
Use the OS secure keystore (Android Keystore or iOS Keychain). Tie access to user authentication or biometrics if possible. Rotate refresh tokens on use and support revocation. Avoid storing refresh tokens in backups or synced plaintext locations.
Is JWT safe for session tokens?
JWTs are convenient, but be careful: they can’t be revoked unless you add server-side checks (revocation list or token versioning). Keep JWT lifetime short and validate signatures using securely stored keys. For sensitive flows, prefer server-side sessions.
Should mobile apps implement certificate pinning?
Pinning adds protection against some Man-in-the-Middle attacks but complicates updates and ops. If you pin, plan for key rotation and provide a safe fallback path. Many teams opt for robust TLS configuration plus monitoring instead of pinning.
What about biometric login?
Biometrics provide good UX for re-auth and local unlocking of secure storage. Use them to gate token access for sensitive actions. Remember: biometrics authenticate the device/user locally—they don’t replace server-side authorization checks.