Security is not a feature you add at the end — it is a property of every decision you make during development. This guide covers the most impactful security practices for Android apps in 2025, organized by the categories where most vulnerabilities originate.

Secure Data Storage

• EncryptedSharedPreferences / EncryptedFile — use the Jetpack Security library to encrypt sensitive local data with a key managed by Android Keystore.
• Never store secrets in plaintext — no passwords, tokens, or API keys in SharedPreferences, SQLite, or files without encryption.
• Use DataStore over SharedPreferences — DataStore can be paired with encrypted storage and is harder to corrupt.

val masterKey = MasterKey.Builder(context)
    .setKeyScheme(MasterKey.KeyScheme.AES256_GCM)
    .build()

val encryptedPrefs = EncryptedSharedPreferences.create(
    context, "secure_prefs", masterKey,
    EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
    EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
)

Network Security

• Certificate pinning — pin your server's certificate in res/xml/network_security_config.xml or via OkHttp's CertificatePinner.
• No cleartext traffic — set android:usesCleartextTraffic="false" in your manifest.
• Validate server certificates — never disable SSL validation in production builds.

Authentication and Authorization

• Use Biometric API for local authentication — fingerprint, face, or device credential.
• Store OAuth tokens in EncryptedSharedPreferences or Keystore, never in memory longer than needed.
• Implement token refresh with a short-lived access token and longer-lived refresh token.

Permission Management

• Request only the permissions your app actually needs. Remove unused permission declarations from the manifest.
• Use the minimum permission (e.g., READ_MEDIA_IMAGES instead of READ_EXTERNAL_STORAGE).
• Handle permission denial gracefully — never block the whole app, provide a path forward.

Code and Build Security

• Enable R8/ProGuard in release builds to shrink and obfuscate your code.
• Remove all debug logging in release builds — use BuildConfig.DEBUG guards.
• Verify all exported components (android:exported) are intentional and protected with permissions where needed.
• Use SafetyNet / Play Integrity API for server-side verification if your app handles high-value transactions.

Security Testing

• Run MobSF (Mobile Security Framework) for automated static analysis.
• Use a proxy (e.g., Burp Suite) during development to inspect all network traffic.
• Include security review in your code review checklist — not just a one-time audit.