Android App Security: Best Practices for 2025

In 2025, building a functional Android app is only half the battle. Users trust us with their personal data, financial information, and private conversations. A single security vulnerability can shatter that trust, ruin your app's reputation, and expose your users to real-world harm. Security isn't a feature; it's the foundation.

Let's move beyond the basics and dive into the practical, battle-tested security measures every Android developer should be implementing right now.

1. Encrypt Everything: Data at Rest

Any sensitive data you store on the device—user tokens, API keys, personal information, cached data—is a target. If a user's device is compromised, unencrypted data is an open book. The solution is to encrypt it, and thankfully, Jetpack makes this incredibly easy.

The Jetpack Security (Tink) library provides drop-in replacements for standard storage classes. Instead of using SharedPreferences, use EncryptedSharedPreferences. It handles all the complex cryptography behind the scenes.

import androidx.security.crypto.EncryptedSharedPreferences
import androidx.security.crypto.MasterKeys

// 1. Create or retrieve the master key for encryption
val masterKeyAlias = MasterKeys.getOrCreate(MasterKeys.AES256_GCM_SPEC)

// 2. Create the encrypted preferences instance
val sharedPreferences = EncryptedSharedPreferences.create(
    "secret_user_prefs",
    masterKeyAlias,
    applicationContext,
    EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
    EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
)

// 3. Use it just like regular SharedPreferences
with(sharedPreferences.edit()) {
    putString("session_token", "your-super-secret-token")
    apply()
}

2. Lock Down Your Network: Data in Transit

Using HTTPS is a given, but you can go a step further to defeat sophisticated man-in-the-middle (MITM) attacks. Certificate Pinning is the practice of telling your app to only trust a specific server certificate or public key. If an attacker tries to intercept your traffic with their own certificate (even a seemingly valid one), your app will refuse to connect.

The modern way to do this is with a Network Security Configuration file. It's declarative and doesn't require any code changes in your networking library (like OkHttp).

<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
    <domain-config>
        <!-- Only trust our specific certificate for this domain -->
        <domain includeSubdomains="true">api.androshelf.com</domain>
        <pin-set>
            <!-- SHA-256 hash of your server's public key -->
            <pin digest="SHA-256">YOUR_CERTIFICATE_PIN_HERE==</pin>
        </pin-set>
    </domain-config>
</network-security-config>

Don't forget to link this file in your AndroidManifest.xml under the <application> tag: android:networkSecurityConfig="@xml/network_security_config".

3. Harden Your Codebase

Your APK is a treasure trove for attackers. You need to make it as difficult as possible for them to reverse-engineer it.

Enable R8/ProGuard: Make sure code shrinking and obfuscation are enabled for your release builds in build.gradle.kts. Obfuscation renames your classes, methods, and fields to meaningless letters, turning your clean code into spaghetti for an attacker.

buildTypes {
    getByName("release") {
        isMinifyEnabled = true // Enables R8
        proguardFiles(getDefaultProguardFile("proguard-android-optimize.txt"), "proguard-rules.pro")
    }
}

Detect Tampering: As a simple integrity check, you can verify your app's signing certificate at runtime. If someone has repackaged your app with their own certificate, this check will fail, and you can shut down the app or alert your servers.

4. Implement Modern, Secure Authentication

Passwords can be stolen. Two-factor authentication is good, but it's even better to leverage the security hardware already on the device. The Jetpack Biometric library provides a simple, unified API for fingerprint and face authentication.

Using it to protect sensitive actions in your app provides a massive security and UX win.

val promptInfo = BiometricPrompt.PromptInfo.Builder()
    .setTitle("Biometric login for AndroShelf")
    .setSubtitle("Log in using your biometric credential")
    .setNegativeButtonText("Use account password")
    .build()

val biometricPrompt = BiometricPrompt(this, executor,
    object : BiometricPrompt.AuthenticationCallback() {
        override fun onAuthenticationSucceeded(result: BiometricPrompt.AuthenticationResult) {
            super.onAuthenticationSucceeded(result)
            // Authentication was successful! Proceed to the app.
        }
        // ... handle errors and failures
    })

biometricPrompt.authenticate(promptInfo)

By layering these defenses, you create a much more resilient application. No single technique is a silver bullet, but together, they present a formidable challenge to attackers and show your users that you take their security seriously.