How to Securely Hide Sensitive Data in Your Android App: Is Obfuscation Enough?

Hiding Sensitive Data in Obfuscated Code

When deploying your Android application, you may encounter concerns about exposing sensitive data, such as server URLs, in decompiled code. Obfuscation techniques like ProGuard provide some protection, but may not effectively conceal all strings.

String Encryption and Decoding

To address this, consider implementing custom mechanisms for encoding or encrypting the strings. For basic obscurity, you can use the android.util.Base64 class. However, this approach offers limited protection as it can be easily decoded.

For stronger protection, use encryption via the javax.crypto.Cipher class. Choose a symmetric cipher like AES and store the encryption key securely in your app. This method is more tedious than secure, as the key may be exposed within the JAR file.

Modifying Code to Use Encrypted Strings

Modify the code to use the decrypted version of the sensitive string instead of the raw value. This typically involves decrypting the string upon startup or initialization of the relevant class or object. Example:

Before:

<code class="java">public class Foo {
    private String mySecret = "http://example.com";

    ...
}</code>

After:

<code class="java">public class Foo {
    private String encrypted = "..." // Manually created encrypted string
    private String key = "..."; // Encryption key
    private String mySecret = MyDecryptUtil.decrypt(encrypted, key);

    ...
}</code>

Alternative Solutions

Consider using a third-party DRM solution like Google's Licensing Service. This can provide a more secure alternative to self-implemented protection mechanisms, but may have its own limitations and requirements.

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